The m_sasl module in InspIRCd before 2.0.23, when used with a service that supports SASL_EXTERNAL authentication, allows remote attackers to spoof certificate fingerprints and consequently log in as another user via a crafted SASL message.
https://github.com/inspircd/inspircd/commit/74fafb7f11b06747f69f182ad5e3769b665eea7a
http://www.openwall.com/lists/oss-security/2016/09/05/8
http://www.openwall.com/lists/oss-security/2016/09/04/3