Applications could be made to expose sensitive information over the network.
The TLS protocol 1.2 and earlier can encrypt compressed data without properly obfuscating the length of the unencrypted data, which allows man-in-the-middle attackers to obtain plaintext content by observing length differences during a series of guesses in which a provided string potentially matches an unknown string in encrypted and compressed traffic. This is known as a CRIME attack in HTTP. Other protocols layered on top of TLS may also make these attacks practical.
4 July 2013
A security issue affects these releases of Ubuntu and its derivatives:
Applications could be made to expose sensitive information over the network.
The TLS protocol 1.2 and earlier can encrypt compressed data without properly obfuscating the length of the unencrypted data, which allows man-in-the-middle attackers to obtain plaintext content by observing length differences during a series of guesses in which a provided string potentially matches an unknown string in encrypted and compressed traffic. This is known as a CRIME attack in HTTP. Other protocols layered on top of TLS may also make these attacks practical.
This update disables compression for all programs using SSL and TLS provided by the OpenSSL library. To re-enable compression for programs that need compression to communicate with legacy services, define the variable OPENSSL_DEFAULT_ZLIB in the program’s environment.
The problem can be corrected by updating your system to the following package versions:
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
In general, a standard system update will make all the necessary changes.
Vulmon