Vulnerabilities > CVE-2019-13636 - Link Following vulnerability in GNU Patch

047910
CVSS 5.9 - MEDIUM
Attack vector
NETWORK
Attack complexity
HIGH
Privileges required
NONE
Confidentiality impact
NONE
Integrity impact
HIGH
Availability impact
NONE
network
high complexity
gnu
CWE-59
nessus

Summary

In GNU patch through 2.7.6, the following of symlinks is mishandled in certain cases other than input files. This affects inp.c and util.c.

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Symlink Attack
    An attacker positions a symbolic link in such a manner that the targeted user or application accesses the link's endpoint, assuming that it is accessing a file with the link's name. The endpoint file may be either output or input. If the file is output, the result is that the endpoint is modified, instead of a file at the intended location. Modifications to the endpoint file may include appending, overwriting, corrupting, changing permissions, or other modifications. In some variants of this attack the attacker may be able to control the change to a file while in other cases they cannot. The former is especially damaging since the attacker may be able to grant themselves increased privileges or insert false information, but the latter can also be damaging as it can expose sensitive information or corrupt or destroy vital system or application files. Alternatively, the endpoint file may serve as input to the targeted application. This can be used to feed malformed input into the target or to cause the target to process different information, possibly allowing the attacker to control the actions of the target or to cause the target to expose information to the attacker. Moreover, the actions taken on the endpoint file are undertaken with the permissions of the targeted user or application, which may exceed the permissions that the attacker would normally have.
  • Accessing, Modifying or Executing Executable Files
    An attack of this type exploits a system's configuration that allows an attacker to either directly access an executable file, for example through shell access; or in a possible worst case allows an attacker to upload a file and then execute it. Web servers, ftp servers, and message oriented middleware systems which have many integration points are particularly vulnerable, because both the programmers and the administrators must be in synch regarding the interfaces and the correct privileges for each interface.
  • Leverage Executable Code in Non-Executable Files
    An attack of this type exploits a system's trust in configuration and resource files, when the executable loads the resource (such as an image file or configuration file) the attacker has modified the file to either execute malicious code directly or manipulate the target process (e.g. application server) to execute based on the malicious configuration parameters. Since systems are increasingly interrelated mashing up resources from local and remote sources the possibility of this attack occurring is high. The attack can be directed at a client system, such as causing buffer overrun through loading seemingly benign image files, as in Microsoft Security Bulletin MS04-028 where specially crafted JPEG files could cause a buffer overrun once loaded into the browser. Another example targets clients reading pdf files. In this case the attacker simply appends javascript to the end of a legitimate url for a pdf (http://www.gnucitizen.org/blog/danger-danger-danger/) http://path/to/pdf/file.pdf#whatever_name_you_want=javascript:your_code_here The client assumes that they are reading a pdf, but the attacker has modified the resource and loaded executable javascript into the client's browser process. The attack can also target server processes. The attacker edits the resource or configuration file, for example a web.xml file used to configure security permissions for a J2EE app server, adding role name "public" grants all users with the public role the ability to use the administration functionality. The server trusts its configuration file to be correct, but when they are manipulated, the attacker gains full control.
  • Manipulating Input to File System Calls
    An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.

Nessus

  • NASL familyUbuntu Local Security Checks
    NASL idUBUNTU_USN-4071-1.NASL
    descriptionIt was discovered that Patch incorrectly handled certain files. An attacker could possibly use this issue to access sensitive information. (CVE-2019-13636) It was discovered that Patch incorrectly handled certain files. An attacker could possibly use this issue to execute arbitrary code. (CVE-2019-13638). Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-01
    modified2020-06-02
    plugin id127042
    published2019-07-25
    reporterUbuntu Security Notice (C) 2019 Canonical, Inc. / NASL script (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/127042
    titleUbuntu 16.04 LTS / 18.04 LTS / 19.04 : patch vulnerabilities (USN-4071-1)
    code
    #
    # (C) Tenable Network Security, Inc.
    #
    # The descriptive text and package checks in this plugin were
    # extracted from Ubuntu Security Notice USN-4071-1. The text 
    # itself is copyright (C) Canonical, Inc. See 
    # <http://www.ubuntu.com/usn/>. Ubuntu(R) is a registered 
    # trademark of Canonical, Inc.
    #
    
    include("compat.inc");
    
    if (description)
    {
      script_id(127042);
      script_version("1.4");
      script_cvs_date("Date: 2019/09/24 11:01:33");
    
      script_cve_id("CVE-2019-13636", "CVE-2019-13638");
      script_xref(name:"USN", value:"4071-1");
    
      script_name(english:"Ubuntu 16.04 LTS / 18.04 LTS / 19.04 : patch vulnerabilities (USN-4071-1)");
      script_summary(english:"Checks dpkg output for updated package.");
    
      script_set_attribute(
        attribute:"synopsis", 
        value:"The remote Ubuntu host is missing a security-related patch."
      );
      script_set_attribute(
        attribute:"description", 
        value:
    "It was discovered that Patch incorrectly handled certain files. An
    attacker could possibly use this issue to access sensitive
    information. (CVE-2019-13636)
    
    It was discovered that Patch incorrectly handled certain files. An
    attacker could possibly use this issue to execute arbitrary code.
    (CVE-2019-13638).
    
    Note that Tenable Network Security has extracted the preceding
    description block directly from the Ubuntu security advisory. Tenable
    has attempted to automatically clean and format it as much as possible
    without introducing additional issues."
      );
      script_set_attribute(
        attribute:"see_also",
        value:"https://usn.ubuntu.com/4071-1/"
      );
      script_set_attribute(attribute:"solution", value:"Update the affected patch package.");
      script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:C/I:C/A:C");
      script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
      script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H");
      script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
      script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
      script_set_attribute(attribute:"exploit_available", value:"true");
    
      script_set_attribute(attribute:"plugin_type", value:"local");
      script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:patch");
      script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04");
      script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
      script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:19.04");
    
      script_set_attribute(attribute:"vuln_publication_date", value:"2019/07/17");
      script_set_attribute(attribute:"patch_publication_date", value:"2019/07/24");
      script_set_attribute(attribute:"plugin_publication_date", value:"2019/07/25");
      script_set_attribute(attribute:"generated_plugin", value:"current");
      script_end_attributes();
    
      script_category(ACT_GATHER_INFO);
      script_copyright(english:"Ubuntu Security Notice (C) 2019 Canonical, Inc. / NASL script (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.");
      script_family(english:"Ubuntu Local Security Checks");
    
      script_dependencies("ssh_get_info.nasl");
      script_require_keys("Host/cpu", "Host/Ubuntu", "Host/Ubuntu/release", "Host/Debian/dpkg-l");
    
      exit(0);
    }
    
    
    include("audit.inc");
    include("ubuntu.inc");
    include("misc_func.inc");
    
    if ( ! get_kb_item("Host/local_checks_enabled") ) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
    release = get_kb_item("Host/Ubuntu/release");
    if ( isnull(release) ) audit(AUDIT_OS_NOT, "Ubuntu");
    release = chomp(release);
    if (! preg(pattern:"^(16\.04|18\.04|19\.04)$", string:release)) audit(AUDIT_OS_NOT, "Ubuntu 16.04 / 18.04 / 19.04", "Ubuntu " + release);
    if ( ! get_kb_item("Host/Debian/dpkg-l") ) audit(AUDIT_PACKAGE_LIST_MISSING);
    
    cpu = get_kb_item("Host/cpu");
    if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
    if ("x86_64" >!< cpu && cpu !~ "^i[3-6]86$") audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "Ubuntu", cpu);
    
    flag = 0;
    
    if (ubuntu_check(osver:"16.04", pkgname:"patch", pkgver:"2.7.5-1ubuntu0.16.04.2")) flag++;
    if (ubuntu_check(osver:"18.04", pkgname:"patch", pkgver:"2.7.6-2ubuntu1.1")) flag++;
    if (ubuntu_check(osver:"19.04", pkgname:"patch", pkgver:"2.7.6-3ubuntu0.1")) flag++;
    
    if (flag)
    {
      security_report_v4(
        port       : 0,
        severity   : SECURITY_HOLE,
        extra      : ubuntu_report_get()
      );
      exit(0);
    }
    else
    {
      tested = ubuntu_pkg_tests_get();
      if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
      else audit(AUDIT_PACKAGE_NOT_INSTALLED, "patch");
    }
    
  • NASL familyHuawei Local Security Checks
    NASL idEULEROS_SA-2020-1317.NASL
    descriptionAccording to the version of the patch package installed, the EulerOS installation on the remote host is affected by the following vulnerability : - In GNU patch through 2.7.6, the following of symlinks is mishandled in certain cases other than input files. This affects inp.c and util.c.(CVE-2019-13636) Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-05-06
    modified2020-03-23
    plugin id134808
    published2020-03-23
    reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/134808
    titleEulerOS 2.0 SP5 : patch (EulerOS-SA-2020-1317)
  • NASL familyGentoo Local Security Checks
    NASL idGENTOO_GLSA-201908-22.NASL
    descriptionThe remote host is affected by the vulnerability described in GLSA-201908-22 (Patch: Multiple vulnerabilities) Multiple vulnerabilities have been discovered in Patch. Please review the CVE identifiers referenced below for details. Impact : A local attacker could pass a specially crafted diff file to Patch, possibly resulting in a Denial of Service condition or arbitrary code execution. Workaround : There is no known workaround at this time.
    last seen2020-06-01
    modified2020-06-02
    plugin id127971
    published2019-08-20
    reporterThis script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/127971
    titleGLSA-201908-22 : Patch: Multiple vulnerabilities
  • NASL familyHuawei Local Security Checks
    NASL idEULEROS_SA-2020-1171.NASL
    descriptionAccording to the version of the patch package installed, the EulerOS installation on the remote host is affected by the following vulnerability : - In GNU patch through 2.7.6, the following of symlinks is mishandled in certain cases other than input files. This affects inp.c and util.c.(CVE-2019-13636) Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-05-03
    modified2020-02-25
    plugin id134005
    published2020-02-25
    reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/134005
    titleEulerOS 2.0 SP8 : patch (EulerOS-SA-2020-1171)
  • NASL familyPhotonOS Local Security Checks
    NASL idPHOTONOS_PHSA-2019-3_0-0025_PATCH.NASL
    descriptionAn update of the patch package has been released.
    last seen2020-06-01
    modified2020-06-02
    plugin id128739
    published2019-09-12
    reporterThis script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/128739
    titlePhoton OS 3.0: Patch PHSA-2019-3.0-0025
  • NASL familyDebian Local Security Checks
    NASL idDEBIAN_DSA-4489.NASL
    descriptionImre Rad discovered several vulnerabilities in GNU patch, leading to shell command injection or escape from the working directory and access and overwrite files, if specially crafted patch files are processed. This update includes a bugfix for a regression introduced by the patch to address CVE-2018-1000156 when applying an ed-style patch (#933140).
    last seen2020-06-01
    modified2020-06-02
    plugin id127102
    published2019-07-29
    reporterThis script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/127102
    titleDebian DSA-4489-1 : patch - security update
  • NASL familyPhotonOS Local Security Checks
    NASL idPHOTONOS_PHSA-2019-2_0-0172_PATCH.NASL
    descriptionAn update of the patch package has been released.
    last seen2020-06-01
    modified2020-06-02
    plugin id128712
    published2019-09-12
    reporterThis script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/128712
    titlePhoton OS 2.0: Patch PHSA-2019-2.0-0172
  • NASL familyDebian Local Security Checks
    NASL idDEBIAN_DLA-1856.NASL
    descriptionHandling of symlinks in patch, a tool to apply a diff file to an original, was wrong in certain cases. For Debian 8
    last seen2020-06-01
    modified2020-06-02
    plugin id126833
    published2019-07-22
    reporterThis script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/126833
    titleDebian DLA-1856-1 : patch security update
  • NASL familyHuawei Local Security Checks
    NASL idEULEROS_SA-2020-1540.NASL
    descriptionAccording to the version of the patch package installed, the EulerOS Virtualization for ARM 64 installation on the remote host is affected by the following vulnerability : - In GNU patch through 2.7.6, the following of symlinks is mishandled in certain cases other than input files. This affects inp.c and util.c.(CVE-2019-13636) Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-05-08
    modified2020-05-01
    plugin id136243
    published2020-05-01
    reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/136243
    titleEulerOS Virtualization for ARM 64 3.0.2.0 : patch (EulerOS-SA-2020-1540)
  • NASL familyHuawei Local Security Checks
    NASL idEULEROS_SA-2020-1335.NASL
    descriptionAccording to the version of the patch package installed, the EulerOS Virtualization for ARM 64 installation on the remote host is affected by the following vulnerability : - In GNU patch through 2.7.6, the following of symlinks is mishandled in certain cases other than input files. This affects inp.c and util.c.(CVE-2019-13636) Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-04-07
    modified2020-04-02
    plugin id135122
    published2020-04-02
    reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/135122
    titleEulerOS Virtualization for ARM 64 3.0.6.0 : patch (EulerOS-SA-2020-1335)

Redhat

advisories
bugzilla
id1732781
titleCVE-2019-13636 patch: the following of symlinks in inp.c and util.c is mishandled in cases other than input files
oval
OR
  • commentRed Hat Enterprise Linux must be installed
    ovaloval:com.redhat.rhba:tst:20070304026
  • AND
    • commentRed Hat Enterprise Linux 8 is installed
      ovaloval:com.redhat.rhba:tst:20193384074
    • OR
      • AND
        • commentpatch-debugsource is earlier than 0:2.7.6-11.el8
          ovaloval:com.redhat.rhsa:tst:20201852001
        • commentpatch-debugsource is signed with Red Hat redhatrelease2 key
          ovaloval:com.redhat.rhsa:tst:20192798002
      • AND
        • commentpatch is earlier than 0:2.7.6-11.el8
          ovaloval:com.redhat.rhsa:tst:20201852003
        • commentpatch is signed with Red Hat redhatrelease2 key
          ovaloval:com.redhat.rhsa:tst:20181199002
rhsa
idRHSA-2020:1852
released2020-04-28
severityModerate
titleRHSA-2020:1852: patch security and bug fix update (Moderate)
rpms
  • patch-0:2.7.6-11.el8
  • patch-debuginfo-0:2.7.6-11.el8
  • patch-debugsource-0:2.7.6-11.el8