ID CVE-2015-7496
Summary GNOME Display Manager (gdm) before 3.18.2 allows physically proximate attackers to bypass the lock screen by holding the Escape key.
References
Vulnerable Configurations
  • Fedora Project Fedora 23
    cpe:2.3:o:fedoraproject:fedora:23
  • cpe:2.3:a:gnome:gnome_display_manager:3.18.0
    cpe:2.3:a:gnome:gnome_display_manager:3.18.0
CVSS
Base: 7.2 (as of 25-11-2015 - 12:07)
Impact:
Exploitability:
CWE CWE-264
CAPEC
  • 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.
  • Blue Boxing
    This type of attack against older telephone switches and trunks has been around for decades. A tone is sent by an adversary to impersonate a supervisor signal which has the effect of rerouting or usurping command of the line. While the US infrastructure proper may not contain widespread vulnerabilities to this type of attack, many companies are connected globally through call centers and business process outsourcing. These international systems may be operated in countries which have not upgraded Telco infrastructure and so are vulnerable to Blue boxing. Blue boxing is a result of failure on the part of the system to enforce strong authorization for administrative functions. While the infrastructure is different than standard current applications like web applications, there are historical lessons to be learned to upgrade the access control for administrative functions.
  • Restful Privilege Elevation
    Rest uses standard HTTP (Get, Put, Delete) style permissions methods, but these are not necessarily correlated generally with back end programs. Strict interpretation of HTTP get methods means that these HTTP Get services should not be used to delete information on the server, but there is no access control mechanism to back up this logic. This means that unless the services are properly ACL'd and the application's service implementation are following these guidelines then an HTTP request can easily execute a delete or update on the server side. The attacker identifies a HTTP Get URL such as http://victimsite/updateOrder, which calls out to a program to update orders on a database or other resource. The URL is not idempotent so the request can be submitted multiple times by the attacker, additionally, the attacker may be able to exploit the URL published as a Get method that actually performs updates (instead of merely retrieving data). This may result in malicious or inadvertent altering of data on the server.
  • Target Programs with Elevated Privileges
    This attack targets programs running with elevated privileges. The attacker would try to leverage a bug in the running program and get arbitrary code to execute with elevated privileges. For instance an attacker would look for programs that write to the system directories or registry keys (such as HKLM, which stores a number of critical Windows environment variables). These programs are typically running with elevated privileges and have usually not been designed with security in mind. Such programs are excellent exploit targets because they yield lots of power when they break. The malicious user try to execute its code at the same level as a privileged system call.
  • 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.
Access
VectorComplexityAuthentication
LOCAL LOW NONE
Impact
ConfidentialityIntegrityAvailability
COMPLETE COMPLETE COMPLETE
nessus via4
  • NASL family Huawei Local Security Checks
    NASL id EULEROS_SA-2017-1173.NASL
    description According to the version of the gdm packages installed, the EulerOS installation on the remote host is affected by the following vulnerability : - It was found that gdm could crash due to a signal handler dispatched to an invalid conversation. An attacker could crash gdm by holding the escape key when the screen is locked, possibly bypassing the locked screen. (CVE-2015-7496) 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 seen 2017-10-29
    modified 2017-09-08
    plugin id 103011
    published 2017-09-08
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=103011
    title EulerOS 2.0 SP1 : gdm (EulerOS-SA-2017-1173)
  • NASL family Huawei Local Security Checks
    NASL id EULEROS_SA-2017-1174.NASL
    description According to the version of the gdm package installed, the EulerOS installation on the remote host is affected by the following vulnerability : - It was found that gdm could crash due to a signal handler dispatched to an invalid conversation. An attacker could crash gdm by holding the escape key when the screen is locked, possibly bypassing the locked screen. (CVE-2015-7496) 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 seen 2017-10-29
    modified 2017-09-08
    plugin id 103012
    published 2017-09-08
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=103012
    title EulerOS 2.0 SP2 : gdm (EulerOS-SA-2017-1174)
  • NASL family Fedora Local Security Checks
    NASL id FEDORA_2015-271025C598.NASL
    description This update fixes CVE-2015-7496 - lock screen bypass when holding escape key. Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen 2017-10-29
    modified 2016-03-04
    plugin id 89180
    published 2016-03-04
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=89180
    title Fedora 23 : gdm-3.18.2-1.fc23 (2015-271025c598)
  • NASL family Red Hat Local Security Checks
    NASL id REDHAT-RHSA-2017-2128.NASL
    description An update for gdm and gnome-session is now available for Red Hat Enterprise Linux 7. Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section. The GNOME Display Manager (GDM) provides the graphical login screen shown shortly after boot up, log out, and when user-switching. The following packages have been upgraded to a later upstream version: gdm (3.22.3), gnome-session (3.22.3). (BZ#1386862, BZ#1386957) Security Fix(es) : * It was found that gdm could crash due to a signal handler dispatched to an invalid conversation. An attacker could crash gdm by holding the escape key when the screen is locked, possibly bypassing the locked screen. (CVE-2015-7496) Additional Changes : For detailed information on changes in this release, see the Red Hat Enterprise Linux 7.4 Release Notes linked from the References section.
    last seen 2017-10-29
    modified 2017-08-07
    plugin id 102113
    published 2017-08-02
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=102113
    title RHEL 7 : gdm and gnome-session (RHSA-2017:2128)
  • NASL family CentOS Local Security Checks
    NASL id CENTOS_RHSA-2017-2128.NASL
    description An update for gdm and gnome-session is now available for Red Hat Enterprise Linux 7. Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section. The GNOME Display Manager (GDM) provides the graphical login screen shown shortly after boot up, log out, and when user-switching. The following packages have been upgraded to a later upstream version: gdm (3.22.3), gnome-session (3.22.3). (BZ#1386862, BZ#1386957) Security Fix(es) : * It was found that gdm could crash due to a signal handler dispatched to an invalid conversation. An attacker could crash gdm by holding the escape key when the screen is locked, possibly bypassing the locked screen. (CVE-2015-7496) Additional Changes : For detailed information on changes in this release, see the Red Hat Enterprise Linux 7.4 Release Notes linked from the References section.
    last seen 2017-10-29
    modified 2017-08-25
    plugin id 102753
    published 2017-08-25
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=102753
    title CentOS 7 : gdm / gnome-session (CESA-2017:2128)
  • NASL family Oracle Linux Local Security Checks
    NASL id ORACLELINUX_ELSA-2017-2128.NASL
    description From Red Hat Security Advisory 2017:2128 : An update for gdm and gnome-session is now available for Red Hat Enterprise Linux 7. Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section. The GNOME Display Manager (GDM) provides the graphical login screen shown shortly after boot up, log out, and when user-switching. The following packages have been upgraded to a later upstream version: gdm (3.22.3), gnome-session (3.22.3). (BZ#1386862, BZ#1386957) Security Fix(es) : * It was found that gdm could crash due to a signal handler dispatched to an invalid conversation. An attacker could crash gdm by holding the escape key when the screen is locked, possibly bypassing the locked screen. (CVE-2015-7496) Additional Changes : For detailed information on changes in this release, see the Red Hat Enterprise Linux 7.4 Release Notes linked from the References section.
    last seen 2017-10-29
    modified 2017-08-09
    plugin id 102297
    published 2017-08-09
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=102297
    title Oracle Linux 7 : gdm / gnome-session (ELSA-2017-2128)
  • NASL family Scientific Linux Local Security Checks
    NASL id SL_20170802_GDM_AND_GNOME_SESSION_ON_SL7_X.NASL
    description The following packages have been upgraded to a later upstream version: gdm (3.22.3), gnome-session (3.22.3). Security Fix(es) : - It was found that gdm could crash due to a signal handler dispatched to an invalid conversation. An attacker could crash gdm by holding the escape key when the screen is locked, possibly bypassing the locked screen. (CVE-2015-7496)
    last seen 2017-10-29
    modified 2017-08-22
    plugin id 102662
    published 2017-08-22
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=102662
    title Scientific Linux Security Update : gdm and gnome-session on SL7.x x86_64
  • NASL family FreeBSD Local Security Checks
    NASL id FREEBSD_PKG_68847B208DDC11E5B69CC86000169601.NASL
    description Ray Strode reports : CVE-2015-7496 - lock screen bypass when holding escape key.
    last seen 2017-10-29
    modified 2015-11-30
    plugin id 86922
    published 2015-11-19
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=86922
    title FreeBSD : gdm -- lock screen bypass when holding escape key (68847b20-8ddc-11e5-b69c-c86000169601)
redhat via4
advisories
bugzilla
id 1449632
title Fuzzy translations in de, es, fr, it, ja, ko, pt_BR, ru, zh_CN, zh_TW
oval
AND
  • OR
    • comment Red Hat Enterprise Linux 7 Client is installed
      oval oval:com.redhat.rhsa:tst:20140675001
    • comment Red Hat Enterprise Linux 7 Server is installed
      oval oval:com.redhat.rhsa:tst:20140675002
    • comment Red Hat Enterprise Linux 7 Workstation is installed
      oval oval:com.redhat.rhsa:tst:20140675003
    • comment Red Hat Enterprise Linux 7 ComputeNode is installed
      oval oval:com.redhat.rhsa:tst:20140675004
  • OR
    • AND
      • comment gnome-session is earlier than 0:3.22.3-4.el7
        oval oval:com.redhat.rhsa:tst:20172128005
      • comment gnome-session is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20172128006
    • AND
      • comment gnome-session-custom-session is earlier than 0:3.22.3-4.el7
        oval oval:com.redhat.rhsa:tst:20172128007
      • comment gnome-session-custom-session is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20172128008
    • AND
      • comment gnome-session-xsession is earlier than 0:3.22.3-4.el7
        oval oval:com.redhat.rhsa:tst:20172128009
      • comment gnome-session-xsession is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20172128010
    • AND
      • comment gdm is earlier than 1:3.22.3-11.el7
        oval oval:com.redhat.rhsa:tst:20172128011
      • comment gdm is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20110395006
    • AND
      • comment gdm-devel is earlier than 1:3.22.3-11.el7
        oval oval:com.redhat.rhsa:tst:20172128013
      • comment gdm-devel is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20172128014
rhsa
id RHSA-2017:2128
released 2017-08-01
severity Moderate
title RHSA-2017:2128: gdm and gnome-session security, bug fix, and enhancement update (Moderate)
rpms
  • gnome-session-0:3.22.3-4.el7
  • gnome-session-custom-session-0:3.22.3-4.el7
  • gnome-session-xsession-0:3.22.3-4.el7
  • gdm-1:3.22.3-11.el7
  • gdm-devel-1:3.22.3-11.el7
refmap via4
confirm
fedora FEDORA-2015-271025c598
mlist
  • [oss-security] 20151117 CVE request for Gnome gdm/screen lock crash
  • [oss-security] 20151117 Re: CVE request for Gnome gdm/screen lock crash
Last major update 25-11-2015 - 12:49
Published 24-11-2015 - 15:59
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