Atheme IRC Services before 7.2.12, when used in conjunction with InspIRCd, allows authentication bypass by ending an IRC handshake at a certain point during a challenge-response login sequence.
https://www.openwall.com/lists/oss-security/2022/01/30/4
https://github.com/atheme/atheme/compare/v7.2.11...v7.2.12
https://github.com/atheme/atheme/commit/4e664c75d0b280a052eb8b5e81aa41944e593c52