An old inffast.c optimization turns out to not be optimal anymore with modern compilers, and furthermore was not compliant with the C standard, for which decrementing a pointer before its allocated memory is undefined.

External References:

https://wiki.mozilla.org/images/0/09/Zlib-report.pdf https://docs.google.com/document/d/10i1KZS5so8xDqH2rplRa2xet0tyTvvJlLbQQmZIUIKE/edit#heading=h.t13tvnx4loq7

Upstream patch:

https://github.com/madler/zlib/commit/9aaec95e82117c1cb0f9624264c3618fc380cecb

CVE assignment:

http://seclists.org/oss-sec/2016/q4/602

Last updated 14 January 2026

As per Upstream advisory:

A double free bug was discovered when OpenSSL parses malformed DSA private keys and could lead to a DoS attack or memory corruption for applications that receive DSA private keys from untrusted sources. This scenario is considered rare.

This issue affects OpenSSL versions 1.0.2 and 1.0.1.

OpenSSL 1.0.2 users should upgrade to 1.0.2g OpenSSL 1.0.1 users should upgrade to 1.0.1s

This issue was reported to OpenSSL on 7th February 2016 by Adam Langley (Google/BoringSSL) using libFuzzer. The fix was developed by Dr Stephen Henson of OpenSSL.

Unspecified vulnerability in Oracle MySQL 5.6.29 and earlier and 5.7.11 and earlier allows remote attackers to affect confidentiality, integrity, and availability via vectors related to Pluggable Authentication.