The manager_dispatch_notify_fd function in systemd allows local users to cause a denial of service (system hang) via a zero-length message received over a notify socket, which causes an error to be returned and the notification handler to be disabled.

An update for systemd is now available for Red Hat Enterprise Linux 7.1 Extended Update Support.

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 systemd packages contain systemd, a system and service manager for Linux, compatible with the SysV and LSB init scripts. It provides aggressive parallelism capabilities, uses socket and D-Bus activation for starting services, offers on-demand starting of daemons, and keeps track of processes using Linux cgroups. In addition, it supports snapshotting and restoring of the system state, maintains mount and automount points, and implements an elaborate transactional dependency-based service control logic. It can also work as a drop-in replacement for sysvinit.

Security Fix(es) :

* A flaw was found in the way systemd handled empty notification messages. A local attacker could use this flaw to make systemd freeze its execution, preventing further management of system services, system shutdown, or zombie process collection via systemd.
(CVE-2016-7796)

This update for systemd fixes the following security issue :

  - CVE-2016-7796: A zero-length message received over     systemd's notification socket could make     manager_dispatch_notify_fd() return an error and, as a     side effect, disable the notification handler     completely. As the notification socket is     world-writable, this could have allowed a local user to     perform a denial-of-service attack against systemd.
    (bsc#1001765)

Additionally, the following non-security fixes are included :

  - Fix HMAC calculation when appending a data object to     journal. (bsc#1000435)

  - Never accept file descriptors from file systems with     mandatory locking enabled. (bsc#954374)

  - Do not warn about missing install info with 'preset'.
    (bsc#970293) 

  - Save /run/systemd/users/UID before starting     user@.service. (bsc#996269)

  - Make sure that /var/lib/systemd/sysv-convert/database is     always initialized. (bsc#982211)

  - Remove daylight saving time handling and tzfile parser.
    (bsc#990074)

  - Make sure directory watch is started before cryptsetup.
    (bsc#987173)

  - Introduce sd_pid_notify() and sd_pid_notifyf() APIs.
    (bsc#987857)

  - Set KillMode=mixed for our daemons that fork worker     processes.

  - Add nosuid and nodev options to tmp.mount.

  - Don't start console-getty.service when /dev/console is     missing. (bsc#982251)

  - Correct segmentation fault in udev/path_id due to     missing NULL check. (bsc#982210)

This update was imported from the SUSE:SLE-12-SP1:Update update project.

This update for systemd fixes the following issues :

  - CVE-2016-7796: A zero-length message received over     systemd's notification socket could make     manager_dispatch_notify_fd() return an error and, as a     side effect, disable the notification handler     completely. As the notification socket is     world-writable, this could have allowed a local user to     perform a denial-of-service attack against systemd.
    (bsc#1001765)

Additionally, the following non-security fixes are included :

  - Fix HMAC calculation when appending a data object to     journal. (bsc#1000435)

  - Never accept file descriptors from file systems with     mandatory locking enabled. (bsc#954374)

  - Do not warn about missing install info with 'preset'.
    (bsc#970293) 

  - Save /run/systemd/users/UID before starting     user@.service. (bsc#996269)

  - Make sure that /var/lib/systemd/sysv-convert/database is     always initialized. (bsc#982211)

This update for systemd fixes the following security issue :

  - CVE-2016-7796: A zero-length message received over     systemd's notification socket could make     manager_dispatch_notify_fd() return an error and, as a     side effect, disable the notification handler     completely. As the notification socket is     world-writable, this could have allowed a local user to     perform a denial-of-service attack against systemd.
    (bsc#1001765) Additionally, the following non-security     fixes are included :

  - Fix HMAC calculation when appending a data object to     journal. (bsc#1000435)

  - Never accept file descriptors from file systems with     mandatory locking enabled. (bsc#954374)

  - Do not warn about missing install info with 'preset'.
    (bsc#970293)

  - Save /run/systemd/users/UID before starting     user@.service. (bsc#996269)

  - Make sure that /var/lib/systemd/sysv-convert/database is     always initialized. (bsc#982211)

  - Remove daylight saving time handling and tzfile parser.
    (bsc#990074)

  - Make sure directory watch is started before cryptsetup.
    (bsc#987173)

  - Introduce sd_pid_notify() and sd_pid_notifyf() APIs.
    (bsc#987857)

  - Set KillMode=mixed for our daemons that fork worker     processes.

  - Add nosuid and nodev options to tmp.mount.

  - Don't start console-getty.service when /dev/console is     missing. (bsc#982251)

  - Correct segmentation fault in udev/path_id due to     missing NULL check. (bsc#982210)

Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Type	Severity
96306	RHEL 7 : systemd (RHSA-2017:0003)	Nessus	Red Hat Local Security Checks	Local	medium
94090	openSUSE Security Update : systemd (openSUSE-2016-1194)	Nessus	SuSE Local Security Checks	Local	medium
94060	openSUSE Security Update : systemd (openSUSE-2016-1184)	Nessus	SuSE Local Security Checks	Local	medium
93937	SUSE SLED12 / SLES12 Security Update : systemd (SUSE-SU-2016:2476-1)	Nessus	SuSE Local Security Checks	Local	medium
93936	SUSE SLES12 Security Update : systemd (SUSE-SU-2016:2475-1)	Nessus	SuSE Local Security Checks	Local	medium

Detections

Analytics

CVE-2016-7796

medium

Tenable Plugins

medium

medium

medium

medium

medium