{"id":"CVE-2026-41059","aliases":["BIT-oauth2-proxy-2026-41059","GHSA-pxq7-h93f-9jrg","GO-2026-5559"],"url":"https://o3.security/vulnerability/CVE-2026-41059","summary":"OAuth2 Proxy has an Authentication Bypass via Fragment Confusion in skip_auth_routes and skip_auth_regex","details":"OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 have a configuration-dependent authentication bypass. Deployments are affected when all of the following are true: Use of `skip_auth_routes` or the legacy `skip_auth_regex`; use of patterns that can be widened by attacker-controlled suffixes, such as `^/foo/.*/bar$` causing potential exposure of `/foo/secret`; and protected upstream applications that interpret `#` as a fragment delimiter or otherwise route the request to the protected base path. In deployments that rely on these settings, an unauthenticated attacker can send a crafted request containing a number sign in the path, including the browser-safe encoded form `%23`, so that OAuth2 Proxy matches a public allowlist rule while the backend serves a protected resource. Deployments that do not use these skip-auth options, or that only allow exact public paths with tightly scoped method and path rules, are not affected. A fix has been implemented in version 7.15.2 to normalize request paths more conservatively before skip-auth matching so fragment content does not influence allowlist decisions. Users who cannot upgrade immediately can reduce exposure by tightening or removing `skip_auth_routes` and `skip_auth_regex` rules, especially patterns that use broad wildcards across path segments. Recommended mitigations include replacing broad rules with exact, anchored public paths and explicit HTTP methods; rejecting requests whose path contains `%23` or `#` at the ingress, load balancer, or WAF level; and/or avoiding placing sensitive application paths behind broad `skip_auth_routes` rules.","published":"2026-04-21T23:17:46.743Z","modified":"2026-07-31T18:30:49.087513138Z","cvss":{"score":8.2,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Go","name":"github.com/oauth2-proxy/oauth2-proxy/v7","fixedVersion":"7.15.2"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41059.json"},{"type":"ADVISORY","url":"https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-pxq7-h93f-9jrg"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-41059"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-31T18:30:49.087513138Z"}}