{"id":"CVE-2020-28042","aliases":["GHSA-v5rv-hpxg-8x49"],"url":"https://o3.security/vulnerability/CVE-2020-28042","summary":"Signature validation bypass in ServiceStack","details":"ServiceStack before 5.9.2 mishandles JWT signature verification unless an application has a custom ValidateToken function that establishes a valid minimum length for a signature.","published":"2020-11-02T21:15:31.320Z","modified":"2026-07-08T20:42:18.068159Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":3,"affectedPackages":[{"ecosystem":"NuGet","name":"ServiceStack","fixedVersion":"5.9.2"}],"fix":{"url":"https://github.com/ServiceStack/ServiceStack/commit/540d4060e877a03ae95343c1a8560a26768585ee","label":"ServiceStack/ServiceStack@540d406"},"references":[{"type":"ADVISORY","url":"https://forums.servicestack.net/t/servicestack-v5-9-2-released/8850"},{"type":"FIX","url":"https://github.com/ServiceStack/ServiceStack/commit/540d4060e877a03ae95343c1a8560a26768585ee"},{"type":"EVIDENCE","url":"https://www.shielder.it/advisories/servicestack-jwt-signature-verification-bypass/"},{"type":"EVIDENCE","url":"https://www.shielder.it/blog/2020/11/re-discovering-a-jwt-authentication-bypass-in-servicestack/"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T20:42:18.068159Z"}}