The mm_newkeys_from_blob function in monitor_wrap.c in sshd in OpenSSH 6.2 and 6.3, when an AES-GCM cipher is used, does not properly initialize memory for a MAC context data structure, which allows remote authenticated users to bypass intended ForceCommand and login-shell restrictions via packet data that provides a crafted callback address.

openssh was updated to fix a memory corruption when AES-GCM is used which could lead to remote code execution after successful authentication. (CVE-2013-4548)

New openssh packages are available for Slackware 14.1 and -current to fix a security issue.

According to its banner, the version of OpenSSH running on the remote host is version 6.2 or 6.3.  It is, therefore, affected by a memory corruption vulnerability in post-authentication when the AES-GCM cipher is used for the key exchange.  Exploitation of this vulnerability could lead to arbitrary code execution. 

Note that installations are only vulnerable if built against an OpenSSL library that supports AES-GCM.

Versions of OpenSSH server before 6.4 may contain a memory corruption vulnerability that exists in the post-authentication 'sshd' process when an AES-GCM cipher is selected during key exchange. This issue can be exploited to execute arbitrary code with the privileges of an authenticated user and bypass restricted shell/command configurations.

Note: NNM has solely relied on the banner of the SSH client to perform this check. Any backported patches or workarounds such as recompiling or edited configurations are not observable through the banner.

Versions of OpenSSH server before 6.4 may contain a memory corruption vulnerability that exists in the post-authentication 'sshd' process when an AES-GCM cipher is selected during key exchange. This issue can be exploited to execute arbitrary code with the privileges of an authenticated user and bypass restricted shell/command configurations.

Note: PVS has solely relied on the banner of the SSH client to perform this check. Any backported patches or workarounds such as recompiling or edited configurations are not observable through the banner.

Markus Friedl discovered that OpenSSH incorrectly handled memory when the AES-GCM cipher was used. A remote authenticated attacker could use this issue to execute arbitrary code as their user, possibly bypassing shell or command restrictions.

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu 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
75204	openSUSE Security Update : openssh (openSUSE-SU-2013:1726-1)	Nessus	SuSE Local Security Checks	Local	medium
73308	AIX OpenSSH Vulnerability : openssh_advisory3.asc	Nessus	AIX Local Security Checks	Local	medium
70952	Slackware 14.1 / current : openssh (SSA:2013-322-02)	Nessus	Slackware Local Security Checks	Local	medium
70895	OpenSSH 6.2 and 6.3 AES-GCM Cipher Memory Corruption	Nessus	Misc.	Remote	medium
8051	OpenSSH v6.2 / v6.3 Remote Memory Corruption Vulnerability	Nessus Network Monitor	SSH		medium
8050	OpenSSH 6.2 / 6.3 Remote Memory Corruption Vulnerability	Nessus Network Monitor	SSH		medium
70798	Ubuntu 13.10 : openssh vulnerability (USN-2014-1)	Nessus	Ubuntu Local Security Checks	Local	medium

Detections

Analytics

CVE-2013-4548

medium

Tenable Plugins

medium

medium

medium

medium

medium

medium

medium