Four security issues have been discovered in Openssl. Below are the relevant snippets from the advisory below.
"1. Certain ASN.1 encodings that are rejected as invalid by the parser can trigger a bug in the deallocation of the corresponding data structure, corrupting the stack. This can be used as a denial of service attack. It is currently unknown whether this can be exploited to run malicious code. This issue does not affect OpenSSL 0.9.6.
2. Unusual ASN.1 tag values can cause an out of bounds read under certain circumstances, resulting in a denial of service vulnerability.
3. A malformed public key in a certificate will crash the verify code if it is set to ignore public key decoding errors. Public key decode errors are not normally ignored, except for debugging purposes, so this is unlikely to affect production code. Exploitation of an affected application would result in a denial of service vulnerability.
4. Due to an error in the SSL/TLS protocol handling, a server will parse a client certificate when one is not specifically requested. This by itself is not strictly speaking a vulnerability but it does mean that *all* SSL/TLS servers that use OpenSSL can be attacked using vulnerabilities 1, 2 and 3 even if they don't enable client authentication."