Description:
A vulnerability was reported in OpenSSL. A remote user can decrypt transmitted data in certain cases.
A remote user that can monitor the network and can capture a long duration 3DES CBC mode encrypted session over which some amount of known plaintext is communicated can recover some plaintext in certain cases.
Over the duration of a long-lived connection, a cipher block collision may occur, allowing the remote user to recover the exclusive OR between the two plaintext blocks. If the communications protocol sends a fixed plaintext portion (e.g., a secure cookie) repeatedly and also sends some amount of known plaintext, the user can recover the secret plaintext.
[Editor's note: The report confirms a successful attack to recover secure HTTP cookies by capturing 785 GB of network traffic.]
The attack method is known as a SWEET32 attack.
64-bit block ciphers, such as 3DES and Blowfish, are affected by this type of attack.
The original advisory will be presented at the 23rd ACM Conference on Computer and Communications Security and is available at:
https://sweet32.info/SWEET32_CCS16.pdf
Karthikeyan Bhargavan and Gaetan Leurent from INRIA reported this vulnerability.
Impact:
A remote user that can monitor the network can decrypt transmitted data in certain cases.
Solution:
[Editor's note: The vulnerability is a known limitation of the cryptographic protocol.]
The vendor has issued a version (1.1.0) that disables the vulnerable 3DES cipher suites in the default configuration.
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