XML Encryption is used for securing communications between Web services by many companies, including IBM, Microsoft and Red Hat. Researchers Juraj Somorovsky and Tibor Jager from the Ruhr University of Bochum (RUB) in Germany, that decrypts data secured with the DES (Data Encryption Standard) or the AES (Advanced Encryption Standard) in CBC (cipher block chaining) mode. They plan to present their findings in more detail at the ACM Conference on Computer and Communications Security later this year.

According to Jörg Schwenk who teaches of Electrical Engineering and Information Technology at RUB, all data encryption algorithms recommended in the XML Encryption standard are affected by this attack, which relies on sending modified ciphertexts to the server and analyzing the errors for clues.

The same technique was by used security researchers Juliano Rizzo and Thai Duong in their ASP.NET Framework padding oracle attack, which earned them this year's Pwnie award for best server-side bug. More recently, the researchers demonstrated a separate attack against SSL/TLS (Secure Sockets Layer/Transfer Layer Security) implementations that use CBC mode, much like this one.

"All of these algorithms are vulnerable to the attacks since they use the CBC mode. So all implementations of the standard should be affected," Schwenk said, referring to the XML Encryption recommendations.

The RUB researchers notified affected vendors through the mailing list of the World Wide Web Consortium (W3C), the organization that drafted the standard. The attack was successfully tested against many implementations used by companies that responded to the researchers' report.