Jenkins 2.218 and earlier, LTS 2.204.1 and earlier does not use a constant-time comparison when checking whether two HMACs are equal. This could potentially allow attackers to use statistical methods to obtain a valid HMAC for an attacker-controlled input value.
Jenkins 2.219, LTS 2.204.2 now uses a constant-time comparison when validating HMACs.
References:- https://nvd.nist.gov/vuln/detail/CVE-2020-2102
- https://access.redhat.com/errata/RHBA-2020:0402
- https://access.redhat.com/errata/RHBA-2020:0675
- https://access.redhat.com/errata/RHSA-2020:0681
- https://access.redhat.com/errata/RHSA-2020:0683
- https://jenkins.io/security/advisory/2020-01-29/#SECURITY-1660
- http://www.openwall.com/lists/oss-security/2020/01/29/1
- https://github.com/jenkinsci/jenkins/commit/6f35dbb939ebe947bdb1979010b208480f1d0e31
- https://github.com/advisories/GHSA-fj6f-6933-839j