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TITLE:
OpenSSH Legacy Certificates Stack Memory Leak Weakness

SECUNIA ADVISORY ID:
SA43181

VERIFY ADVISORY:
Secunia.com
http://secunia.com/advisories/43181/
Customer Area (Credentials Required)
https://ca.secunia.com/?page=viewadvisory&vuln_id=43181

RELEASE DATE:
2011-02-08

DISCUSS ADVISORY:
http://secunia.com/advisories/43181/#comments

AVAILABLE ON SITE AND IN CUSTOMER AREA:
 * Last Update
 * Popularity
 * Comments
 * Criticality Level
 * Impact
 * Where
 * Solution Status
 * Operating System / Software
 * CVE Reference(s)

http://secunia.com/advisories/43181/

ONLY AVAILABLE IN CUSTOMER AREA:
 * Authentication Level
 * Report Reliability
 * Secunia PoC
 * Secunia Analysis
 * Systems Affected
 * Approve Distribution
 * Remediation Status
 * Secunia CVSS Score
 * CVSS

https://ca.secunia.com/?page=viewadvisory&vuln_id=43181

ONLY AVAILABLE WITH SECUNIA CSI AND SECUNIA PSI:
 * AUTOMATED SCANNING

http://secunia.com/vulnerability_scanning/personal/
http://secunia.com/vulnerability_scanning/corporate/wsus_sccm_3rd_third_party_patching/

DESCRIPTION:
A weakness has been reported in OpenSSH, which can be exploited by
malicious people to disclose potentially sensitive information.

The weakness is caused due to OpenSSH not properly initialising 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.

The weakness is reported in versions 5.6 and 5.7.

SOLUTION:
Update to version 5.8 or apply the patch (see vendor's advisory for
additional details). Rotate the CA key for legacy certificates
generated with a vulnerable version.

PROVIDED AND/OR DISCOVERED BY:
The vendor credits Mateusz Kocielski.

ORIGINAL ADVISORY:
OpenSSH:
http://www.openssh.com/txt/legacy-cert.adv
http://www.openssh.com/txt/release-5.8

OTHER REFERENCES:
Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

DEEP LINKS:
Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

EXTENDED DESCRIPTION:
Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

EXTENDED SOLUTION:
Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

EXPLOIT:
Further details available in Customer Area:
http://secunia.com/products/corporate/EVM/

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About:
This Advisory was delivered by Secunia as a free service to help
private users keeping their systems up to date against the latest
vulnerabilities.

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Please Note:
Secunia recommends that you verify all advisories you receive by
clicking the link.
Secunia NEVER sends attached files with advisories.
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use those supplied by the vendor.

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