PuTTY Information for VU#958563

SSH CBC vulnerability



Vendor Statement

The latest release (0.60) of PuTTY will always preferentially select CTR-mode ciphers over CBC-mode, and cannot even be configured by the user to do otherwise. Therefore, it is immune to this vulnerability when talking to any server which supports CTR mode.

    Development snapshots of PuTTY beginning with 2008-11-27 will contain a countermeasure which avoids leaking information through this attack even when operating in CBC mode. Future releases of PuTTY will also contain this countermeasure.

    (That is, the countermeasures will prevent PuTTY from leaking information about data previously sent from the server to the client. Protecting data sent from client to server, such as passwords, must be done by the server.)

    We are currently not treating this vulnerability as severe enough to warrant an emergency security release.

    Vendor Information

    The vendor has not provided us with any further information regarding this vulnerability.

    Vendor References



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