USN-204-1: SSL library vulnerability

Publication date

14 October 2005

Overview

SSL library vulnerability


Details

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 “machine-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.

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 “machine-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

In general, a standard system update will make all the necessary changes.

Learn more about how to get the fixes.

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

Ubuntu Release Package Version
5.10 breezy libssl0.9.7 – 
5.04 hoary libssl0.9.7 – 
4.10 warty libssl0.9.7 – 

Reduce your security exposure

Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines.


Have additional questions?

Talk to a member of the team ›