Technical Description

Multiple vulnerabilities have been identified in OpenSSH, which could be exploited by remote attackers to cause a denial of service, disclose sensitive information, or potentially execute arbitrary commands.

The first flaw is due to an error in the CRC compensation attack detection algorithm when processing packets with multiple identical blocks, which could be exploited by attackers to exhaust all available resources via a specially crafted SSH packet, creating a denial of service condition.

The second vulnerability is due to a GSSAPI authentication abort, which could be exploited by remote attackers to determine the validity of usernames on certain platforms.

The third flaw is due to a race condition in the signal handler, which could be exploited by remote unauthenticated attackers to cause a denial of service. On portable versions with GSSAPI authentication enabled, this vulnerability could be exploited by unauthenticated remote attackers to execute arbitrary commands.

Affected Products

OpenSSH version 4.3 and prior

Solution

Upgrade to OpenSSH version 4.4 :
http://www.openssh.com/ftp.html

References

http://www.vupen.com/english/advisories/2006/3777
http://bugs.gentoo.org/show_bug.cgi?id=148228

Credits

Vulnerabilities reported by Tavis Ormandy (Google Security Team) and Mark Dowd.

ChangeLog

2006-09-26 : Initial release
2006-09-27 : Updated Advisory

Vulnerability Management

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