Updated OpenSSL packages are available that fix a potential timing-based attack. [Updated 12 March 2003] Added packages for CentOS Linux ES and CentOS Linux WS
OpenSSL is a commercial-grade, full-featured, open source toolkit which implements the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) protocols as well as a full-strength, general purpose cryptography library. In a paper, Brice Canvel, Alain Hiltgen, Serge Vaudenay, and Martin Vuagnoux describe and demonstrate a timing-based attack on CBC ciphersuites in SSL and TLS. An active attacker may be able to use timing observations to distinguish between two different error cases: cipher padding errors and MAC verification errors. Over multiple connections this can leak sufficient information to be able to retrieve the plaintext of a common, fixed block. In order for an attack to be sucessful an attacker must be able to act as a man-in-the-middle to intercept and modify multiple connections which all involve a common fixed plaintext block (such as a password), and have good network conditions that allow small changes in timing to be reliably observed. These updated packages contain a patch provided by the OpenSSL group that corrects this vulnerability. Because server applications are affected by these vulnerabilities, we advise users to restart all services that use OpenSSL functionality or alternatively reboot their systems after installing these updates.