CVE-2016-7796: Input Validation
First published: Wed Oct 05 2016(Updated: )
It was found that systemd fails an assertion in manager_invoke_notify_message() when a zero-length message is received over its notification socket, causing it to no longer perform it's expected functionality. This issue was assigned <a href="https://access.redhat.com/security/cve/CVE-2016-7795">CVE-2016-7795</a> and is tracked via <a class="bz_bug_link bz_status_CLOSED bz_closed bz_public " title="CLOSED ERRATA - CVE-2016-7795 systemd: Assertion failure when PID 1 receives a zero-length message over notify socket" href="show_bug.cgi?id=1380286">bug 1380286</a>. Upstream bug report is: <a href="https://github.com/systemd/systemd/issues/4234">https://github.com/systemd/systemd/issues/4234</a> Older systemd versions either don't include the assert that is triggered in manager_invoke_notify_message(), or have manager_process_notify_fd() function return error before calling manager_invoke_notify_message(). That error return still causes systemd to exit its main loop and freeze its execution in a similar way it's done in newer versions after failed assertion. <a href="https://github.com/systemd/systemd/issues/4234#issuecomment-250441246">https://github.com/systemd/systemd/issues/4234#issuecomment-250441246</a> The manager_invoke_notify_message() function with assert was introduced in version v209: <a href="https://github.com/systemd/systemd/commit/5ba6985b6c8ef85a8bcfeb1b65239c863436e75b#diff-ab78220e12703ee63fa1e6a2caa16bebR1319">https://github.com/systemd/systemd/commit/5ba6985b6c8ef85a8bcfeb1b65239c863436e75b#diff-ab78220e12703ee63fa1e6a2caa16bebR1319</a> However, the assertion was not reachable before the error return was removed in v219: <a href="https://github.com/systemd/systemd/commit/d875aa8ce10b458dc218c0d98f4a82c8904d6d03">https://github.com/systemd/systemd/commit/d875aa8ce10b458dc218c0d98f4a82c8904d6d03</a> The systemd versions in Red Hat Enterprise Linux 7.0 and 7.1 are based on upstream v208, but include manager_invoke_notify_message() added via a separate backported patch. The assertion is not reachable, so those versions are affected by <a href="https://access.redhat.com/security/cve/CVE-2016-7796">CVE-2016-7796</a>, but not affected by <a href="https://access.redhat.com/security/cve/CVE-2016-7795">CVE-2016-7795</a>. Red Hat Enterprise Linux 7.2 rebased systemd to version v219. Therefore, those packages are no longer affected by <a href="https://access.redhat.com/security/cve/CVE-2016-7796">CVE-2016-7796</a>, but are now affected by <a href="https://access.redhat.com/security/cve/CVE-2016-7795">CVE-2016-7795</a>.
Credit: cve@mitre.org cve@mitre.org
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Systemd Project Systemd | =209 | |
| Systemd Project Systemd | =213 | |
| Systemd Project Systemd | =214 | |
| Systemd Project Systemd | =229 | |
| Novell Suse Linux Enterprise Software Development Kit | =12.0-sp1 | |
| Novell Suse Linux Enterprise Desktop | =12-sp1 | |
| Novell Suse Linux Enterprise Server | =12.0 | |
| Novell Suse Linux Enterprise Server | =12.0-sp1 | |
| Novell Suse Linux Enterprise Server For Sap | =12.0 | |
| Redhat Enterprise Linux Desktop | =7.0 | |
| Redhat Enterprise Linux Hpc Node | =7.0 | |
| Redhat Enterprise Linux Server | =7.0 | |
| Redhat Enterprise Linux Workstation | =7.0 |
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Reference Links
- https://access.redhat.com/security/cve/CVE-2016-7795
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1380286
- https://github.com/systemd/systemd/issues/4234
- https://github.com/systemd/systemd/issues/4234#issuecomment-250441246
- https://github.com/systemd/systemd/commit/5ba6985b6c8ef85a8bcfeb1b65239c863436e75b#diff-ab78220e12703ee63fa1e6a2caa16bebR1319
- https://github.com/systemd/systemd/commit/d875aa8ce10b458dc218c0d98f4a82c8904d6d03
- https://access.redhat.com/security/cve/CVE-2016-7796
- https://rhn.redhat.com/errata/RHBA-2015-2092.html
- https://rhn.redhat.com/errata/RHSA-2017-0003.html
- https://bugzilla.redhat.com/show_bug.cgi?id=1381911
- http://lists.opensuse.org/opensuse-security-announce/2016-10/msg00015.html
- http://lists.opensuse.org/opensuse-security-announce/2016-10/msg00016.html
- http://rhn.redhat.com/errata/RHSA-2017-0003.html
- http://www.openwall.com/lists/oss-security/2016/09/30/1
- http://www.securityfocus.com/bid/93250
- http://www.securitytracker.com/id/1037320
- https://www.agwa.name/blog/post/how_to_crash_systemd_in_one_tweet
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