Vulnerabilities > CVE-2020-7040 - Link Following vulnerability in multiple products

047910
CVSS 8.1 - HIGH
Attack vector
NETWORK
Attack complexity
HIGH
Privileges required
NONE
Confidentiality impact
HIGH
Integrity impact
HIGH
Availability impact
HIGH
network
high complexity
storebackup
debian
opensuse
canonical
CWE-59
nessus

Summary

storeBackup.pl in storeBackup through 3.5 relies on the /tmp/storeBackup.lock pathname, which allows symlink attacks that possibly lead to privilege escalation. (Local users can also create a plain file named /tmp/storeBackup.lock to block use of storeBackup until an admin manually deletes that file.)

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 familySuSE Local Security Checks
    NASL idOPENSUSE-2020-119.NASL
    descriptionThis update for storeBackup fixes the following issues : - CVE-2020-7040: Fixed a symlink attack which could lead to denial of service (boo#1156767).
    last seen2020-06-01
    modified2020-06-02
    plugin id133341
    published2020-01-30
    reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/133341
    titleopenSUSE Security Update : storeBackup (openSUSE-2020-119)
    code
    #
    # (C) Tenable Network Security, Inc.
    #
    # The descriptive text and package checks in this plugin were
    # extracted from openSUSE Security Update openSUSE-2020-119.
    #
    # The text description of this plugin is (C) SUSE LLC.
    #
    
    include("compat.inc");
    
    if (description)
    {
      script_id(133341);
      script_version("1.4");
      script_cvs_date("Date: 2020/02/12");
    
      script_cve_id("CVE-2020-7040");
    
      script_name(english:"openSUSE Security Update : storeBackup (openSUSE-2020-119)");
      script_summary(english:"Check for the openSUSE-2020-119 patch");
    
      script_set_attribute(
        attribute:"synopsis", 
        value:"The remote openSUSE host is missing a security update."
      );
      script_set_attribute(
        attribute:"description", 
        value:
    "This update for storeBackup fixes the following issues :
    
      - CVE-2020-7040: Fixed a symlink attack which could lead
        to denial of service (boo#1156767)."
      );
      script_set_attribute(
        attribute:"see_also",
        value:"https://bugzilla.opensuse.org/show_bug.cgi?id=1156767"
      );
      script_set_attribute(
        attribute:"solution", 
        value:"Update the affected storeBackup 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:U/RL:OF/RC:C");
      script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H");
      script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
      script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
    
      script_set_attribute(attribute:"plugin_type", value:"local");
      script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:opensuse:storeBackup");
      script_set_attribute(attribute:"cpe", value:"cpe:/o:novell:opensuse:15.1");
    
      script_set_attribute(attribute:"vuln_publication_date", value:"2020/01/21");
      script_set_attribute(attribute:"patch_publication_date", value:"2020/01/28");
      script_set_attribute(attribute:"plugin_publication_date", value:"2020/01/30");
      script_set_attribute(attribute:"generated_plugin", value:"current");
      script_end_attributes();
    
      script_category(ACT_GATHER_INFO);
      script_copyright(english:"This script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.");
      script_family(english:"SuSE Local Security Checks");
    
      script_dependencies("ssh_get_info.nasl");
      script_require_keys("Host/local_checks_enabled", "Host/SuSE/release", "Host/SuSE/rpm-list");
    
      exit(0);
    }
    
    
    include("audit.inc");
    include("global_settings.inc");
    include("rpm.inc");
    
    if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
    release = get_kb_item("Host/SuSE/release");
    if (isnull(release) || release =~ "^(SLED|SLES)") audit(AUDIT_OS_NOT, "openSUSE");
    if (release !~ "^(SUSE15\.1)$") audit(AUDIT_OS_RELEASE_NOT, "openSUSE", "15.1", release);
    if (!get_kb_item("Host/SuSE/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);
    
    
    
    flag = 0;
    
    if ( rpm_check(release:"SUSE15.1", reference:"storeBackup-3.5-lp151.5.3.1") ) flag++;
    
    if (flag)
    {
      if (report_verbosity > 0) security_hole(port:0, extra:rpm_report_get());
      else security_hole(0);
      exit(0);
    }
    else
    {
      tested = pkg_tests_get();
      if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
      else audit(AUDIT_PACKAGE_NOT_INSTALLED, "storeBackup");
    }
    
  • NASL familyDebian Local Security Checks
    NASL idDEBIAN_DLA-2095.NASL
    descriptionstoreBackup.pl in storeBackup through 3.5 relies on the /tmp/storeBackup.lock pathname, which allows symlink attacks that possibly lead to privilege escalation. Local users can also create a plain file named /tmp/storeBackup.lock to block use of storeBackup until an admin manually deletes that file. For Debian 8
    last seen2020-06-01
    modified2020-06-02
    plugin id133509
    published2020-02-06
    reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/133509
    titleDebian DLA-2095-1 : storebackup security update
    code
    #
    # (C) Tenable Network Security, Inc.
    #
    # The descriptive text and package checks in this plugin were
    # extracted from Debian Security Advisory DLA-2095-1. The text
    # itself is copyright (C) Software in the Public Interest, Inc.
    #
    
    include("compat.inc");
    
    if (description)
    {
      script_id(133509);
      script_version("1.3");
      script_cvs_date("Date: 2020/02/13");
    
      script_cve_id("CVE-2020-7040");
    
      script_name(english:"Debian DLA-2095-1 : storebackup security update");
      script_summary(english:"Checks dpkg output for the updated package.");
    
      script_set_attribute(
        attribute:"synopsis", 
        value:"The remote Debian host is missing a security update."
      );
      script_set_attribute(
        attribute:"description", 
        value:
    "storeBackup.pl in storeBackup through 3.5 relies on the
    /tmp/storeBackup.lock pathname, which allows symlink attacks that
    possibly lead to privilege escalation.
    
    Local users can also create a plain file named /tmp/storeBackup.lock
    to block use of storeBackup until an admin manually deletes that file.
    
    For Debian 8 'Jessie', this problem has been fixed in version
    3.2.1-1+deb8u1.
    
    We recommend that you upgrade your storebackup packages.
    
    NOTE: Tenable Network Security has extracted the preceding description
    block directly from the DLA 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://lists.debian.org/debian-lts-announce/2020/02/msg00003.html"
      );
      script_set_attribute(
        attribute:"see_also",
        value:"https://packages.debian.org/source/jessie/storebackup"
      );
      script_set_attribute(
        attribute:"solution", 
        value:"Upgrade the affected storebackup 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:U/RL:OF/RC:C");
      script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H");
      script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
      script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
    
      script_set_attribute(attribute:"plugin_type", value:"local");
      script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:storebackup");
      script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:8.0");
    
      script_set_attribute(attribute:"vuln_publication_date", value:"2020/01/21");
      script_set_attribute(attribute:"patch_publication_date", value:"2020/02/05");
      script_set_attribute(attribute:"plugin_publication_date", value:"2020/02/06");
      script_set_attribute(attribute:"generated_plugin", value:"current");
      script_end_attributes();
    
      script_category(ACT_GATHER_INFO);
      script_copyright(english:"This script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.");
      script_family(english:"Debian Local Security Checks");
    
      script_dependencies("ssh_get_info.nasl");
      script_require_keys("Host/local_checks_enabled", "Host/Debian/release", "Host/Debian/dpkg-l");
    
      exit(0);
    }
    
    
    include("audit.inc");
    include("debian_package.inc");
    
    
    if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
    if (!get_kb_item("Host/Debian/release")) audit(AUDIT_OS_NOT, "Debian");
    if (!get_kb_item("Host/Debian/dpkg-l")) audit(AUDIT_PACKAGE_LIST_MISSING);
    
    
    flag = 0;
    if (deb_check(release:"8.0", prefix:"storebackup", reference:"3.2.1-1+deb8u1")) flag++;
    
    if (flag)
    {
      if (report_verbosity > 0) security_hole(port:0, extra:deb_report_get());
      else security_hole(0);
      exit(0);
    }
    else audit(AUDIT_HOST_NOT, "affected");