Vulnerabilities > CVE-2006-3741 - Unspecified vulnerability in Linux Kernel

047910
CVSS 0.0 - NONE
Attack vector
UNKNOWN
Attack complexity
UNKNOWN
Privileges required
UNKNOWN
Confidentiality impact
UNKNOWN
Integrity impact
UNKNOWN
Availability impact
UNKNOWN
linux
nessus

Summary

The perfmonctl system call (sys_perfmonctl) in Linux kernel 2.4.x and 2.6 before 2.6.18, when running on Itanium systems, does not properly track the reference count for file descriptors, which allows local users to cause a denial of service (file descriptor consumption).

Vulnerable Configurations

Part Description Count
OS
Linux
285

Nessus

  • NASL familySuSE Local Security Checks
    NASL idSUSE_KERNEL-BIGSMP-2399.NASL
    descriptionThis kernel update fixes the following security problems : - A bug within the UDF filesystem that caused machine hangs when truncating files on the filesystem was fixed. [#186226]. (CVE-2006-4145) - A potential crash when receiving IPX packets was fixed. This problem is thought not to be exploitable. [#197809] - A problem in DVB packet handling could be used to crash the machine when receiving DVB net packages is active. [#201429]. (CVE-2006-4623) - A struct file leak was fixed in the perfmon(2) system call on the Itanium architecture. [#202269]. (CVE-2006-3741) - A malformed ELF image can be used on the Itanium architecture to trigger a kernel crash (denial of service) when a local attacker can supply it to be started. [#203822]. (CVE-2006-4538) - A problem in the ATM protocol handling clip_mkip function could be used by remote attackers to potentially crash the machine. [#205383]. (CVE-2006-4997) CVE-2006-5757/ - A problem in the grow_buffers function could be used to crash or hang the machine using a corrupted filesystem. This affects filesystem types ISO9660 and NTFS. [#205384]. (CVE-2006-6060) - On the i386 architecture the ELFAGS content was not correctly saved, which could be used by local attackers to crash other programs using the AC and NT flag or to escalate privileges by waiting for iopl privileges to be leaked. [#209386]. (CVE-2006-5173) - On the S/390 architecture copy_from_user() could be used by local attackers to read kernel memory. [#209880]. (CVE-2006-5174) - A problem in IPv6 flowlabel handling can be used by local attackers to hang the machine. [#216590]. (CVE-2006-5619) - On the PowerPC architecture a syscall has been wired without the proper futex implementation that can be exploited by a local attacker to hang the machine. [#217295]. (CVE-2006-5648) - On the PowerPC architecture the proper futex implementation was missing a fix for alignment check which could be used by a local attacker to crash the machine. [#217295]. (CVE-2006-5649) - A problem in cramfs could be used to crash the machine during mounting a crafted cramfs image. This requires an attacker to supply such a crafted image and have a user mount it. [#218237]. (CVE-2006-5823) - A problem in the ext3 filesystem could be used by attackers able to supply a crafted ext3 image to cause a denial of service or further data corruption if a user mounts this image. [#220288]. (CVE-2006-6053) - Missing return code checking in the HFS could be used to crash machine when a user complicit attacker is able to supply a specially crafted HFS image. [#221230]. (CVE-2006-6056) - Multiple unspecified vulnerabilities in netfilter for IPv6 code allow remote attackers to bypass intended restrictions via fragmentation attack vectors, aka (1)
    last seen2020-06-01
    modified2020-06-02
    plugin id29490
    published2007-12-13
    reporterThis script is Copyright (C) 2007-2019 Tenable Network Security, Inc.
    sourcehttps://www.tenable.com/plugins/nessus/29490
    titleSuSE 10 Security Update : Linux kernel (ZYPP Patch Number 2399)
  • NASL familySuSE Local Security Checks
    NASL idSUSE_KERNEL-2397.NASL
    descriptionThis kernel update fixes the following security problems : - CVE-2006-4145: A bug within the UDF filesystem that caused machine hangs when truncating files on the filesystem was fixed. [#186226] - A potential crash when receiving IPX packets was fixed. This problem is thought not to be exploitable. [#197809] - CVE-2006-4623: A problem in DVB packet handling could be used to crash the machine when receiving DVB net packages is active. [#201429] - CVE-2006-3741: A struct file leak was fixed in the perfmon(2) system call on the Itanium architecture. [#202269] - CVE-2006-4538: A malformed ELF image can be used on the Itanium architecture to trigger a kernel crash (denial of service) when a local attacker can supply it to be started. [#203822] - CVE-2006-4997: A problem in the ATM protocol handling clip_mkip function could be used by remote attackers to potentially crash the machine. [#205383] CVE-2006-5757/ - CVE-2006-6060: A problem in the grow_buffers function could be used to crash or hang the machine using a corrupted filesystem. This affects filesystem types ISO9660 and NTFS. [#205384] - CVE-2006-5173: On the i386 architecture the ELFAGS content was not correctly saved, which could be used by local attackers to crash other programs using the AC and NT flag or to escalate privileges by waiting for iopl privileges to be leaked. [#209386] - CVE-2006-5174: On the S/390 architecture copy_from_user() could be used by local attackers to read kernel memory. [#209880] - CVE-2006-5619: A problem in IPv6 flowlabel handling can be used by local attackers to hang the machine. [#216590] - CVE-2006-5648: On the PowerPC architecture a syscall has been wired without the proper futex implementation that can be exploited by a local attacker to hang the machine. [#217295] - CVE-2006-5649: On the PowerPC architecture the proper futex implementation was missing a fix for alignment check which could be used by a local attacker to crash the machine. [#217295] - CVE-2006-5823: A problem in cramfs could be used to crash the machine during mounting a crafted cramfs image. This requires an attacker to supply such a crafted image and have a user mount it. [#218237] - CVE-2006-6053: A problem in the ext3 filesystem could be used by attackers able to supply a crafted ext3 image to cause a denial of service or further data corruption if a user mounts this image. [#220288] - CVE-2006-6056: Missing return code checking in the HFS could be used to crash machine when a user complicit attacker is able to supply a specially crafted HFS image. [#221230] - CVE-2006-4572: Multiple unspecified vulnerabilities in netfilter for IPv6 code allow remote attackers to bypass intended restrictions via fragmentation attack vectors, aka (1)
    last seen2020-06-01
    modified2020-06-02
    plugin id27291
    published2007-10-17
    reporterThis script is Copyright (C) 2007-2019 Tenable Network Security, Inc.
    sourcehttps://www.tenable.com/plugins/nessus/27291
    titleopenSUSE 10 Security Update : kernel (kernel-2397)
  • NASL familyDebian Local Security Checks
    NASL idDEBIAN_DSA-1233.NASL
    descriptionSeveral local and remote vulnerabilities have been discovered in the Linux kernel that may lead to a denial of service or the execution of arbitrary code. The Common Vulnerabilities and Exposures project identifies the following problems : - CVE-2006-3741 Stephane Eranian discovered a local DoS (Denial of Service) vulnerability on the ia64 architecture. A local user could exhaust the available file descriptors by exploiting a counting error in the permonctl() system call. - CVE-2006-4538 Kirill Korotaev reported a local DoS (Denial of Service) vulnerability on the ia64 and sparc architectures. A user could cause the system to crash by executing a malformed ELF binary due to insufficient verification of the memory layout. - CVE-2006-4813 Dmitriy Monakhov reported a potential memory leak in the __block_prepare_write function. __block_prepare_write does not properly sanitize kernel buffers during error recovery, which could be exploited by local users to gain access to sensitive kernel memory. - CVE-2006-4997 ADLab Venustech Info Ltd reported a potential remote DoS (Denial of Service) vulnerability in the IP over ATM subsystem. A remote system could cause the system to crash by sending specially crafted packets that would trigger an attempt to free an already-freed pointer resulting in a system crash. - CVE-2006-5174 Martin Schwidefsky reported a potential leak of sensitive information on s390 systems. The copy_from_user function did not clear the remaining bytes of the kernel buffer after receiving a fault on the userspace address, resulting in a leak of uninitialized kernel memory. A local user could exploit this by appending to a file from a bad address. - CVE-2006-5619 James Morris reported a potential local DoS (Denial of Service) vulnerability that could be used to hang or oops a system. The seqfile handling for /proc/net/ip6_flowlabel has a flaw that can be exploited to cause an infinite loop by reading this file after creating a flowlabel. - CVE-2006-5649 Fabio Massimo Di Nitto reported a potential remote DoS (Denial of Service) vulnerability on powerpc systems. The alignment exception only checked the exception table for -EFAULT, not for other errors. This can be exploited by a local user to cause a system crash (panic). - CVE-2006-5751 Eugene Teo reported a vulnerability in the get_fdb_entries function that could potentially be exploited to allow arbitrary code execution with escalated privileges. - CVE-2006-5871 Bill Allombert reported that various mount options are ignored by smbfs when UNIX extensions are enabled. This includes the uid, gid and mode options. Client systems would silently use the server-provided settings instead of honoring these options, changing the security model. This update includes a fix from Haroldo Gamal that forces the kernel to honor these mount options. Note that, since the current versions of smbmount always pass values for these options to the kernel, it is not currently possible to activate unix extensions by omitting mount options. However, this behavior is currently consistent with the current behavior of the next Debian release,
    last seen2020-06-01
    modified2020-06-02
    plugin id23846
    published2006-12-14
    reporterThis script is Copyright (C) 2006-2019 Tenable Network Security, Inc.
    sourcehttps://www.tenable.com/plugins/nessus/23846
    titleDebian DSA-1233-1 : kernel-source-2.6.8 - several vulnerabilities
  • NASL familyMandriva Local Security Checks
    NASL idMANDRAKE_MDKSA-2006-182.NASL
    descriptionA number of vulnerabilities were discovered and corrected in the Linux 2.6 kernel : Stephane Eranian discovered an issue with permon2.0 where, under certain circumstances, the perfmonctl() system call may not correctly manage the file descriptor reference count, resulting in the system possibly running out of file structure (CVE-2006-3741). Prior to and including 2.6.17, the Universal Disk Format (UDF) filesystem driver allowed local users to cause a DoS (hang and crash) via certain operations involving truncated files (CVE-2006-4145). Various versions of the Linux kernel allowed local users to cause a DoS (crash) via an SCTP socket with a certain SO_LINGER value, which is possibly related to the patch used to correct CVE-2006-3745 (CVE-2006-4535). The Unidirectional Lightweight Encapsulation (ULE) decapsulation component in the dvb driver allows remote attackers to cause a DoS (crash) via an SNDU length of 0 in a ULE packet (CVE-2006-4623). The provided packages are patched to fix these vulnerabilities. All users are encouraged to upgrade to these updated kernels immediately and reboot to effect the fixes. In addition to these security fixes, other fixes have been included such as : - added support for new devices: o NetXtreme BCM5715 gigabit ethernet o NetXtreme II BCM5708 gigabit ethernet - enabled the CISS driver for Xen kernels - updated ich8 support in ata_piix - enabled support for 1078 type controller in megaraid_sas - multiple fixes for RSBAC support To update your kernel, please follow the directions located at : http://www.mandriva.com/en/security/kernelupdate
    last seen2020-06-01
    modified2020-06-02
    plugin id24567
    published2007-02-18
    reporterThis script is Copyright (C) 2007-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/24567
    titleMandrake Linux Security Advisory : kernel (MDKSA-2006:182)
  • NASL familySuSE Local Security Checks
    NASL idSUSE_KERNEL-DEBUG-2393.NASL
    descriptionThis kernel update fixes the following security problems : - A bug within the UDF filesystem that caused machine hangs when truncating files on the filesystem was fixed. [#186226]. (CVE-2006-4145) - A potential crash when receiving IPX packets was fixed. This problem is thought not to be exploitable. [#197809] - A problem in DVB packet handling could be used to crash the machine when receiving DVB net packages is active. [#201429]. (CVE-2006-4623) - A struct file leak was fixed in the perfmon(2) system call on the Itanium architecture. [#202269]. (CVE-2006-3741) - A malformed ELF image can be used on the Itanium architecture to trigger a kernel crash (denial of service) when a local attacker can supply it to be started. [#203822]. (CVE-2006-4538) - A problem in the ATM protocol handling clip_mkip function could be used by remote attackers to potentially crash the machine. [#205383]. (CVE-2006-4997) CVE-2006-5757/ - A problem in the grow_buffers function could be used to crash or hang the machine using a corrupted filesystem. This affects filesystem types ISO9660 and NTFS. [#205384]. (CVE-2006-6060) - On the i386 architecture the ELFAGS content was not correctly saved, which could be used by local attackers to crash other programs using the AC and NT flag or to escalate privileges by waiting for iopl privileges to be leaked. [#209386]. (CVE-2006-5173) - On the S/390 architecture copy_from_user() could be used by local attackers to read kernel memory. [#209880]. (CVE-2006-5174) - A problem in IPv6 flowlabel handling can be used by local attackers to hang the machine. [#216590]. (CVE-2006-5619) - On the PowerPC architecture a syscall has been wired without the proper futex implementation that can be exploited by a local attacker to hang the machine. [#217295]. (CVE-2006-5648) - On the PowerPC architecture the proper futex implementation was missing a fix for alignment check which could be used by a local attacker to crash the machine. [#217295]. (CVE-2006-5649) - A problem in cramfs could be used to crash the machine during mounting a crafted cramfs image. This requires an attacker to supply such a crafted image and have a user mount it. [#218237]. (CVE-2006-5823) - A problem in the ext3 filesystem could be used by attackers able to supply a crafted ext3 image to cause a denial of service or further data corruption if a user mounts this image. [#220288]. (CVE-2006-6053) - Missing return code checking in the HFS could be used to crash machine when a user complicit attacker is able to supply a specially crafted HFS image. [#221230]. (CVE-2006-6056) - Multiple unspecified vulnerabilities in netfilter for IPv6 code allow remote attackers to bypass intended restrictions via fragmentation attack vectors, aka (1)
    last seen2020-06-01
    modified2020-06-02
    plugin id59162
    published2012-05-17
    reporterThis script is Copyright (C) 2012-2019 Tenable Network Security, Inc.
    sourcehttps://www.tenable.com/plugins/nessus/59162
    titleSuSE 10 Security Update : Linux kernel (ZYPP Patch Number 2393)
  • NASL familyOracle Linux Local Security Checks
    NASL idORACLELINUX_ELSA-2006-0617.NASL
    descriptionUpdated kernel packages that fix security issues are now available. This update has been rated as having important security impact by the Red Hat Security Response Team. The Linux kernel handles the basic functions of the operating system. These new kernel packages contain fixes for the security issues described below : From Red Hat Security Advisory 2006-0617 : * a flaw in the proc file system that allowed a local user to use a suid-wrapper for scripts to gain root privileges (CVE-2006-3626, Important) * a flaw in the SCTP implementation that allowed a local user to cause a denial of service (panic) or to possibly gain root privileges (CVE-2006-3745, Important) * a flaw in NFS exported ext2/ext3 partitions when handling invalid inodes that allowed a remote authenticated user to cause a denial of service (filesystem panic) (CVE-2006-3468, Important) * a flaw in the restore_all code path of the 4/4GB split support of non-hugemem kernels that allowed a local user to cause a denial of service (panic) (CVE-2006-2932, Important) * a flaw in IPv4 netfilter handling for the unlikely use of SNMP NAT processing that allowed a remote user to cause a denial of service (crash) or potential memory corruption (CVE-2006-2444, Moderate) * a flaw in the DVD handling of the CDROM driver that could be used together with a custom built USB device to gain root privileges (CVE-2006-2935, Moderate) * a flaw in the handling of O_DIRECT writes that allowed a local user to cause a denial of service (memory consumption) (CVE-2004-2660, Low) * a flaw in the SCTP chunk length handling that allowed a remote user to cause a denial of service (crash) (CVE-2006-1858, Low) * a flaw in the input handling of the ftdi_sio driver that allowed a local user to cause a denial of service (memory consumption) (CVE-2006-2936, Low) In addition a bugfix was added to enable a clean reboot for the IBM Pizzaro machines. Red Hat would like to thank Wei Wang of McAfee Avert Labs and Kirill Korotaev for reporting issues fixed in this erratum. From Red Hat Security Advisory ELSA-2006-0689 : * a flaw in the SCTP support that allowed a local user to cause a denial of service (crash) with a specific SO_LINGER value. (CVE-2006-4535, Important) * a flaw in the hugepage table support that allowed a local user to cause a denial of service (crash). (CVE-2005-4811, Important) * a flaw in the mprotect system call that allowed setting write permission for a read-only attachment of shared memory. (CVE-2006-2071, Moderate) * a flaw in HID0[31] (en_attn) register handling on PowerPC 970 systems that allowed a local user to cause a denial of service. (crash) (CVE-2006-4093, Moderate) * a flaw in the perfmon support of Itanium systems that allowed a local user to cause a denial of service by consuming all file descriptors. (CVE-2006-3741, Moderate) * a flaw in the ATM subsystem. On systems with installed ATM hardware and configured ATM support, a remote user could cause a denial of service (panic) by accessing socket buffers memory after freeing them. (CVE-2006-4997, Moderate) * a flaw in the DVB subsystem. On systems with installed DVB hardware and configured DVB support, a remote user could cause a denial of service (panic) by sending a ULE SNDU packet with length of 0. (CVE-2006-4623, Low) * an information leak in the network subsystem that possibly allowed a local user to read sensitive data from kernel memory. (CVE-2006-0039, Low) In addition, two bugfixes for the IPW-2200 wireless driver were included. The first one ensures that wireless management applications correctly identify IPW-2200 controlled devices, while the second fix ensures that DHCP requests using the IPW-2200 operate correctly. Red Hat would like to thank Olof Johansson, Stephane Eranian and Solar Designer for reporting issues fixed in this erratum.
    last seen2020-06-01
    modified2020-06-02
    plugin id67401
    published2013-07-12
    reporterThis script is Copyright (C) 2013-2019 Tenable Network Security, Inc.
    sourcehttps://www.tenable.com/plugins/nessus/67401
    titleOracle Linux 4 : kernel (ELSA-2006-0617 / ELSA-2006-0689)
  • NASL familyCentOS Local Security Checks
    NASL idCENTOS_RHSA-2006-0689.NASL
    descriptionUpdated kernel packages that fix several security issues in the Red Hat Enterprise Linux 4 kernel are now available. This security advisory has been rated as having important security impact by the Red Hat Security Response Team. The Linux kernel handles the basic functions of the operating system. These new kernel packages contain fixes for the security issues described below : * a flaw in the SCTP support that allowed a local user to cause a denial of service (crash) with a specific SO_LINGER value. (CVE-2006-4535, Important) * a flaw in the hugepage table support that allowed a local user to cause a denial of service (crash). (CVE-2005-4811, Important) * a flaw in the mprotect system call that allowed setting write permission for a read-only attachment of shared memory. (CVE-2006-2071, Moderate) * a flaw in HID0[31] (en_attn) register handling on PowerPC 970 systems that allowed a local user to cause a denial of service. (crash) (CVE-2006-4093, Moderate) * a flaw in the perfmon support of Itanium systems that allowed a local user to cause a denial of service by consuming all file descriptors. (CVE-2006-3741, Moderate) * a flaw in the ATM subsystem. On systems with installed ATM hardware and configured ATM support, a remote user could cause a denial of service (panic) by accessing socket buffers memory after freeing them. (CVE-2006-4997, Moderate) * a flaw in the DVB subsystem. On systems with installed DVB hardware and configured DVB support, a remote user could cause a denial of service (panic) by sending a ULE SNDU packet with length of 0. (CVE-2006-4623, Low) * an information leak in the network subsystem that possibly allowed a local user to read sensitive data from kernel memory. (CVE-2006-0039, Low) In addition, two bugfixes for the IPW-2200 wireless driver were included. The first one ensures that wireless management applications correctly identify IPW-2200 controlled devices, while the second fix ensures that DHCP requests using the IPW-2200 operate correctly. Red Hat would like to thank Olof Johansson, Stephane Eranian and Solar Designer for reporting issues fixed in this erratum. All Red Hat Enterprise Linux 4 users are advised to upgrade their kernels to the packages associated with their machine architectures and configurations as listed in this erratum.
    last seen2020-06-01
    modified2020-06-02
    plugin id22513
    published2006-10-10
    reporterThis script is Copyright (C) 2006-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/22513
    titleCentOS 4 : kernel (CESA-2006:0689)
  • NASL familyRed Hat Local Security Checks
    NASL idREDHAT-RHSA-2006-0689.NASL
    descriptionUpdated kernel packages that fix several security issues in the Red Hat Enterprise Linux 4 kernel are now available. This security advisory has been rated as having important security impact by the Red Hat Security Response Team. The Linux kernel handles the basic functions of the operating system. These new kernel packages contain fixes for the security issues described below : * a flaw in the SCTP support that allowed a local user to cause a denial of service (crash) with a specific SO_LINGER value. (CVE-2006-4535, Important) * a flaw in the hugepage table support that allowed a local user to cause a denial of service (crash). (CVE-2005-4811, Important) * a flaw in the mprotect system call that allowed setting write permission for a read-only attachment of shared memory. (CVE-2006-2071, Moderate) * a flaw in HID0[31] (en_attn) register handling on PowerPC 970 systems that allowed a local user to cause a denial of service. (crash) (CVE-2006-4093, Moderate) * a flaw in the perfmon support of Itanium systems that allowed a local user to cause a denial of service by consuming all file descriptors. (CVE-2006-3741, Moderate) * a flaw in the ATM subsystem. On systems with installed ATM hardware and configured ATM support, a remote user could cause a denial of service (panic) by accessing socket buffers memory after freeing them. (CVE-2006-4997, Moderate) * a flaw in the DVB subsystem. On systems with installed DVB hardware and configured DVB support, a remote user could cause a denial of service (panic) by sending a ULE SNDU packet with length of 0. (CVE-2006-4623, Low) * an information leak in the network subsystem that possibly allowed a local user to read sensitive data from kernel memory. (CVE-2006-0039, Low) In addition, two bugfixes for the IPW-2200 wireless driver were included. The first one ensures that wireless management applications correctly identify IPW-2200 controlled devices, while the second fix ensures that DHCP requests using the IPW-2200 operate correctly. Red Hat would like to thank Olof Johansson, Stephane Eranian and Solar Designer for reporting issues fixed in this erratum. All Red Hat Enterprise Linux 4 users are advised to upgrade their kernels to the packages associated with their machine architectures and configurations as listed in this erratum.
    last seen2020-06-01
    modified2020-06-02
    plugin id22523
    published2006-10-10
    reporterThis script is Copyright (C) 2006-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/22523
    titleRHEL 4 : kernel (RHSA-2006:0689)

Oval

accepted2013-04-29T04:12:40.463-04:00
classvulnerability
contributors
  • nameAharon Chernin
    organizationSCAP.com, LLC
  • nameDragos Prisaca
    organizationG2, Inc.
definition_extensions
  • commentThe operating system installed on the system is Red Hat Enterprise Linux 4
    ovaloval:org.mitre.oval:def:11831
  • commentCentOS Linux 4.x
    ovaloval:org.mitre.oval:def:16636
  • commentOracle Linux 4.x
    ovaloval:org.mitre.oval:def:15990
descriptionThe perfmonctl system call (sys_perfmonctl) in Linux kernel 2.4.x and 2.6 before 2.6.18, when running on Itanium systems, does not properly track the reference count for file descriptors, which allows local users to cause a denial of service (file descriptor consumption).
familyunix
idoval:org.mitre.oval:def:11250
statusaccepted
submitted2010-07-09T03:56:16-04:00
titleThe perfmonctl system call (sys_perfmonctl) in Linux kernel 2.4.x and 2.6 before 2.6.18, when running on Itanium systems, does not properly track the reference count for file descriptors, which allows local users to cause a denial of service (file descriptor consumption).
version26

Redhat

advisories
rhsa
idRHSA-2006:0689
rpms
  • kernel-0:2.6.9-42.0.3.EL
  • kernel-debuginfo-0:2.6.9-42.0.3.EL
  • kernel-devel-0:2.6.9-42.0.3.EL
  • kernel-doc-0:2.6.9-42.0.3.EL
  • kernel-hugemem-0:2.6.9-42.0.3.EL
  • kernel-hugemem-devel-0:2.6.9-42.0.3.EL
  • kernel-largesmp-0:2.6.9-42.0.3.EL
  • kernel-largesmp-devel-0:2.6.9-42.0.3.EL
  • kernel-smp-0:2.6.9-42.0.3.EL
  • kernel-smp-devel-0:2.6.9-42.0.3.EL