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Insecure Library Loading
Not critical

OpenSSH Two Weaknesses

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Release Date:  2011-02-07    Last Update:  2012-01-27    Views:  3,834

Secunia Advisory SA43181

Where:

From remote

Impact:

Brute force, Exposure of sensitive information

Solution Status:

Vendor Patch

Software:

CVE Reference(s):

Description


Two weaknesses have been reported in OpenSSH, which can be exploited by malicious users and malicious people to disclose potentially sensitive information.

1) OpenSSH does not properly initialise a nonce field with random data when generating legacy certificates ("-t" command line option of ssh-keygen). This can result in certain stack memory being used as nonce, which can lead to the disclosure of potentially sensitive information.

Note: Certificates with user-specified contents may also be less protected against hash collision attacks. However, these attacks are currently not considered practical for the SHA signatures used.

This weakness is reported in versions 5.6 and 5.7.

2) An error within the "auth_parse_options()" function (auth-options.c) can be exploited to e.g. disclose the forced commands configured in the authorized_keys file.

This weakness is reported in versions prior to 5.7-p1.


Solution:
Update to version 5.8. Rotate the CA key for legacy certificates generated with a vulnerable version. Weakness #2 is also fixed in version 5.7-p1.

Provided and/or discovered by:
1) The vendor credits Mateusz Kocielski.
2) Disclosed in a CVS commit.

Original Advisory:
OpenSSH:
http://www.openssh.com/txt/legacy-cert.adv
http://www.openssh.com/txt/release-5.8
http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/auth-options.c.diff?r1=1.53;r2=1.54

Deep Links:
Links available to Secunia VIM customers

Do you have additional information related to this advisory?

Please provide information about patches, mitigating factors, new versions, exploits, faulty patches, links, and other relevant data by posting comments to this Advisory. You can also send this information to vuln@secunia.com

Subject: OpenSSH Two Weaknesses

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