{"id":"CVE-2020-26276","aliases":["GHSA-w3wf-cfx3-6gcx"],"url":"https://o3.security/vulnerability/CVE-2020-26276","summary":"SAML authentication vulnerability due to stdlib XML parsing","details":"Fleet is an open source osquery manager. In Fleet before version 3.5.1, due to issues in Go's standard library XML parsing, a valid SAML response may be mutated by an attacker to modify the trusted document. This can result in allowing unverified logins from a SAML IdP. Users that configure Fleet with SSO login may be vulnerable to this issue. This issue is patched in 3.5.1. The fix was made using https://github.com/mattermost/xml-roundtrip-validator If upgrade to 3.5.1 is not possible, users should disable SSO authentication in Fleet.","published":"2020-12-17T20:15:13.760Z","modified":"2026-07-09T01:30:54.369749Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/fleetdm/fleet/v4","fixedVersion":"3.5.1"}],"fix":{"url":"https://github.com/fleetdm/fleet/commit/57812a532e5f749c8e18c6f6a652eca65c083607","label":"fleetdm/fleet@57812a5"},"references":[{"type":"ADVISORY","url":"https://github.com/fleetdm/fleet/blob/master/CHANGELOG.md#fleet-351-dec-14-2020"},{"type":"ADVISORY","url":"https://github.com/fleetdm/fleet/security/advisories/GHSA-w3wf-cfx3-6gcx"},{"type":"ADVISORY","url":"https://github.com/mattermost/xml-roundtrip-validator"},{"type":"ADVISORY","url":"https://mattermost.com/blog/coordinated-disclosure-go-xml-vulnerabilities"},{"type":"FIX","url":"https://github.com/fleetdm/fleet/commit/57812a532e5f749c8e18c6f6a652eca65c083607"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T01:30:54.369749Z"}}