The OpenSSL Project's developer team has released updates to address six security flaws including one "critical vulnerability" that has been highlighted in the Cipher Block Chaining (CBC) encryption mode. Security is a prime concern for the project given its openly stated aim to create a commercial-grade Open Source toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1).

The project team has issued the following security advisory statement: "Nadhem Alfardan and Kenny Paterson have discovered an extension of the Vaudenay 'padding oracle' attack on CBC mode encryption, which enables an efficient plaintext recovery attack against the OpenSSL implementation of DTLS. Their attack exploits timing differences arising during decryption processing."

Reports suggest that a CBC vulnerability was highlighted at one point last year. This flaw is thought to have come about due to a lack of randomization in the CBC initialization process. The problems have been compounded by additional fears relating to the use of uninitialized memory that have been identified when padding out SSL 3.0 blocks.

Note: In cryptography, an encryption oracle works by encrypting input it receives under certain key. A random oracle always answers with consistently random data; a padding oracle decrypts an input message to inform the system whether the padding was correct.