{"id":"CVE-2021-32813","aliases":["GHSA-m697-4v8f-55qg","GO-2022-0923"],"url":"https://o3.security/vulnerability/CVE-2021-32813","summary":"Header dropping in traefik","details":"# Impact\n\nThere exists a potential header vulnerability in Traefik's handling of the Connection header. Active exploitation of this issue is unlikely, as it requires that a removed header would lead to a privilege escalation, however, the Traefik team has addressed this issue to prevent any potential abuse.\n\n# Details\n\nIf you have a chain of Traefik middlewares, and one of them sets a request header `Important-Security-Header`, then sending a request with the following Connection header will cause it to be removed before the request was sent:\n\n```\ncurl 'https://example.com' -H \"Connection: Important-Security-Header\" -0\n```\n\nIn this case, the backend does not see the request header `Important-Security-Header`.\n\n# Patches\n\nTraefik v2.4.x: https://github.com/traefik/traefik/releases/tag/v2.4.13\n\n# Workarounds\n\nNo.\n\n# For more information\n\nIf you have any questions or comments about this advisory, [open an issue](https://github.com/traefik/traefik/issues).\n","published":"2021-08-03T23:15:07.370Z","modified":"2026-08-07T17:02:10.198247Z","cvss":{"score":8.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Go","name":"github.com/traefik/traefik/v2","fixedVersion":"2.4.13"},{"ecosystem":"Go","name":"github.com/traefik/traefik","fixedVersion":null}],"fix":{"url":"https://github.com/traefik/traefik/pull/8319/commits/cbaf86a93014a969b8accf39301932c17d0d73f9","label":"traefik/traefik#8319"},"references":[{"type":"ADVISORY","url":"https://github.com/traefik/traefik/releases/tag/v2.4.13"},{"type":"ADVISORY","url":"https://github.com/traefik/traefik/security/advisories/GHSA-m697-4v8f-55qg"},{"type":"FIX","url":"https://github.com/traefik/traefik/pull/8319/commits/cbaf86a93014a969b8accf39301932c17d0d73f9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-32813"},{"type":"PACKAGE","url":"github.com/traefik/traefik"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T17:02:10.198247Z"}}