{"id":"CVE-2026-53424","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-53424","summary":"Missing one-time-use enforcement in Samly allows replay of SAML bearer assertions","details":"## Summary\n\nAuthentication Bypass by Capture-replay vulnerability in dropbox samly allows an attacker to authenticate as the subject of a captured SAML assertion by resubmitting it.\n\nSamly.Helper.decode\\_idp\\_auth\\_resp/3 in lib/samly/helper.ex calls esaml\\_sp:validate\\_assertion/2, whose default duplicate detector is a no-op. The /3 arity accepting a DuplicateFun exists in esaml and implements the check, but Samly never calls it and offers no configuration to supply one, so the SAML 2.0 Web Browser SSO Profile requirement that a bearer assertion be used once is unenforced. An attacker holding a valid SAMLResponse obtained from the network, from browser history, or from logs can submit the identical bytes repeatedly until the assertion's NotOnOrAfter passes, each time establishing a session as the assertion's subject.\n\nThis issue affects samly: from 0.3.0 onward.","published":"2026-08-20T17:27:11.115Z","modified":"2026-08-20T18:45:05.958784591Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Hex","name":"samly","fixedVersion":null}],"fix":null,"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-53424.html"},{"type":"PACKAGE","url":"https://hex.pm/packages/samly"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-20T18:45:05.958784591Z"}}