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OpenSSL "NETSCAPE_REUSE_CIPHER_CHANGE_BUG" Ciphersuite Downgrade Vulnerability

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Release Date:  2010-12-03    Last Update:  2010-12-08    Views:  4,928

Secunia Advisory SA42473

Where:

From remote

Impact:

Security Bypass

Solution Status:

Vendor Patch

CVE Reference(s):

Description


A vulnerability has been reported in OpenSSL, which can be exploited by malicious people to bypass certain security restrictions.

The vulnerability is caused due to an error within the "SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG" workaround in the SSL/TLS server code. This can be exploited by e.g. sniffing the session identifier and downgrading the cached ciphersuite prior to the legitimate client resuming the session, potentially leading to the client using a weaker ciphersuite.

Successful exploitation requires that the server uses the internal caching mechanisms of OpenSSL and the "SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG" flag (e.g. enabled via the "SSL_OP_ALL" option).

Note: In versions prior to 0.9.8j, this can further be exploited to force the use of a ciphersuite disabled on the server side.

The vulnerability is reported in all versions prior to 0.9.8q or 1.0.0c.


Solution:
Update to version 0.9.8q or 1.0.0c or apply patches.

Further details available to Secunia VIM customers

Provided and/or discovered by:
The vendor credits Martin Rex.

Original Advisory:
http://www.openssl.org/news/secadv_20101202.txt

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: OpenSSL "NETSCAPE_REUSE_CIPHER_CHANGE_BUG" Ciphersuite Downgrade Vulnerability

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