USN-204-1: SSL library vulnerability

14 October 2005

openssl vulnerability

A security issue affects these releases of Ubuntu and its derivatives:

  • Ubuntu 5.10
  • Ubuntu 5.04
  • Ubuntu 4.10

Software Description


Yutaka Oiwa discovered a possible cryptographic weakness in OpenSSL applications. Applications using the OpenSSL library can use the SSL_OP_MSIE_SSLV2_RSA_PADDING option (or SSL_OP_ALL, which implies the former) to maintain compatibility with third party products, which is achieved by working around known bugs in them.

The SSL_OP_MSIE_SSLV2_RSA_PADDING option disabled a verification step in the SSL 2.0 server supposed to prevent active protocol-version rollback attacks. With this verification step disabled, an attacker acting as a “man in the middle” could force a client and a server to negotiate the SSL 2.0 protocol even if these parties both supported SSL 3.0 or TLS 1.0. The SSL 2.0 protocol is known to have severe cryptographic weaknesses and is supported as a fallback only.

Update instructions

The problem can be corrected by updating your system to the following package versions:

Ubuntu 5.10
Ubuntu 5.04
Ubuntu 4.10

To update your system, please follow these instructions: