{"id":"EEF-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\n`Samly.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.","aliases":["CVE-2026-53424"],"modified":"2026-09-08T05:30:36.653017365Z","published":"2026-08-20T17:27:11.115Z","database_specific":{"capec_ids":["CAPEC-60"],"cpe_ids":["cpe:2.3:a:dropbox:samly:*:*:*:*:*:*:*:*","cpe:2.3:a:handnot2:samly:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-294"]},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-53424.html"},{"type":"PACKAGE","url":"https://hex.pm/packages/samly"}],"affected":[{"package":{"name":"samly","ecosystem":"Hex","purl":"pkg:hex/samly"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.3.0"}]}],"versions":["0.10.0","0.10.1","0.4.0","0.5.0","0.6.0","0.6.1","0.6.2","0.6.3","0.7.0","0.7.1","0.7.2","0.8.0","0.8.1","0.8.2","0.8.3","0.8.4","0.9.0","0.9.1","0.9.2","0.9.3","1.0.0","1.0.0-rc.0","1.0.0-rc.1","1.1.0","1.2.0","1.3.0","1.4.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-53424.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/dropbox/samly","events":[{"introduced":"8a5bb1b4a4753d05470da2036323477f63cfdf4c"}]}],"versions":["v1.0.0","v1.0.0-rc.1","v1.0.0-rc.0","v0.10.1","v0.10.0","v0.9.3","v0.9.1","v0.9.0","v0.8.4","v0.8.3","v0.8.2","v0.8.1","v0.8.0","v0.7.2","v0.7.1","v0.7.0","v0.6.3","v0.6.2","v0.6.1","v0.6.0","v0.5.0","v0.3.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-53424.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/handnot2/samly","events":[{"introduced":"8a5bb1b4a4753d05470da2036323477f63cfdf4c"}]}],"versions":["v1.0.0","v1.0.0-rc.1","v1.0.0-rc.0","v0.10.1","v0.10.0","v0.9.3","v0.9.1","v0.9.0","v0.8.4","v0.8.3","v0.8.2","v0.8.1","v0.8.0","v0.7.2","v0.7.1","v0.7.0","v0.6.3","v0.6.2","v0.6.1","v0.6.0","v0.5.0","v0.3.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-53424.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"}],"credits":[{"name":"Mark Madsen","type":"REPORTER"},{"name":"Jonatan Männchen / EEF","type":"COORDINATOR"}]}