GNOME Display Manager (gdm) before 3.18.2 allows physically proximate attackers to bypass the lock screen by holding the Escape key.

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.

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.

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.

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)

The remote Oracle Linux 7 host has packages installed that are affected by a vulnerability as referenced in the ELSA-2017-2128 advisory.

    gdm     [3.22.3-11]
    - Add japanese translation       Resolves: #1449632

    [3.22.3-10]
    - Add patches to try to maintain some semblance of compatibility       when live upgrading between 7.3 and 7.4       Related: #1448786

    [3.22.3-9]
    - Make sure reauthentication is run within the user       session.
      Resolves:#1448209

    [3.22.3-8]
    - Reap transient login screens when they are no longer needed
    - Jump to login screen if we end up on a blank VT       Resolves: #1301028

    [3.22.3-7]
    - Fix user switching       Related: #1386862

    [3.22.3-6]
    - Fix indirect XDMCP       Resolves: #1273156

    [3.22.3-5]
    - Attempt to fix po file installation       Related: #1386862

    [3.22.3-4]
    - Drop reference to wayland in config file
    - use autosetup to simplify spec maintenance       Related: #1386862

    [3.22.3-3]
    - Don't fall over if autologin user isn't available       Resolves #1373837

    [1:3.22.3-2]
    - Honor anaconda's firstboot being disabled       Resolves: #1226819

    [3.22.3-1]
    - Rebase to 3.22.3       Resolves: #1386862

    [3.14.2-19]
    - Add error traps around XKillClient calls, fixes regression       on logout       Resolves: #1377987

    gnome-session     [3.22.3-4]
    - fix crash in fail whale       Resolves: #1392970

    [3.22.3-3]
    - Fix the ability to disable a service from session properties       Resolves: #1310975

    [3.22.3-2]
    - Drop gnome-xorg.desktop       Related: #1386957

    [3.22.3-1]
    - Rebase to 3.22.3       Resolves: #1386957

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

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.

Ray Strode reports :

CVE-2015-7496 - lock screen bypass when holding escape key.

ID	Name	Product	Family	Severity
103012	EulerOS 2.0 SP2 : gdm (EulerOS-SA-2017-1174)	Nessus	Huawei Local Security Checks	high
103011	EulerOS 2.0 SP1 : gdm (EulerOS-SA-2017-1173)	Nessus	Huawei Local Security Checks	high
102753	CentOS 7 : gdm / gnome-session (CESA-2017:2128)	Nessus	CentOS Local Security Checks	high
102662	Scientific Linux Security Update : gdm and gnome-session on SL7.x x86_64 (20170802)	Nessus	Scientific Linux Local Security Checks	high
102297	Oracle Linux 7 : gdm / and / gnome-session (ELSA-2017-2128)	Nessus	Oracle Linux Local Security Checks	medium
102113	RHEL 7 : gdm and gnome-session (RHSA-2017:2128)	Nessus	Red Hat Local Security Checks	high
89180	Fedora 23 : gdm-3.18.2-1.fc23 (2015-271025c598)	Nessus	Fedora Local Security Checks	high
86922	FreeBSD : gdm -- lock screen bypass when holding escape key (68847b20-8ddc-11e5-b69c-c86000169601)	Nessus	FreeBSD Local Security Checks	high

Detections

Analytics

CVE-2015-7496

medium

Tenable Plugins

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high