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Cisco Bug: CSCum00386 - Unsupported algorithms/ciphers are incorrectly treated as non-SSL

Last Modified

Nov 27, 2020

Products (1)

  • Cisco IronPort Web Security Appliance Software

Known Affected Releases

7.5.2-118 7.7.0-608 8.0.0-Beta1-280

Description (partial)

If the remote server is supporting TLS v1, but not offering any ciphers we support in our probe the WSA treat a connection as non-SSL. 
This will prevent a passthru action on HTTPS proxy in decryption policy to work.

In the case of the customer reporting, the server was accepting only TLSv1 and GOST cipher. WSA do not support yet GOST (CSCzv91934). As a consequence we fail to negotiate SSL handshake. If now blocking of non-SSL on HTTPS port is enabled the session will be dropped even the server and client would support algorithms/ciphers which WSA does not.
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