{"id":"CVE-2026-81509","aliases":["EUVD-2026-110037","GHSA-q64r-v7j5-6hfg"],"status":"published","title":"nforwardauth: Unvalidated r parameter allows post-authentication open redirect","description":"nforwardauth is a forward auth service that allows the use of a single authentication middleware for multiple sites. Versions prior to 1.5.1 accept an unvalidated `r` query parameter on the `/login` endpoint and use them as the post-authentication redirect destination. An unauthenticated attacker can create a legitimate `nforwardauth` login URL that redirects a victim to an attacker-controlled website after the victim successfully authenticates. This issue may facilitate phishing and other social-engineering attacks by abusing the trust associated with the legitimate authentication domain. This vulnerability does not provide an unauthenticated ForwardAuth bypass. Version 1.5.1 contains a patch.","severity":{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00318,"percentile":0.25037,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-601"],"published":"2026-10-26T17:19:15Z","modified":"2026-10-28T03:01:30Z","products":[{"vendor":"nosduco","product":"nforwardauth"}],"references":[{"url":"https://github.com/nosduco/nforwardauth/security/advisories/GHSA-q64r-v7j5-6hfg","tags":["x_refsource_CONFIRM","advisory"]},{"url":"https://github.com/nosduco/nforwardauth/pull/71","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/nosduco/nforwardauth/commit/664f2602f9e1459558d1c4c55019f6d48bc64c43","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/nosduco/nforwardauth/releases/tag/v1.5.1","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81509.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81509","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-81509","title":"nforwardauth: Unvalidated r parameter allows post-authentication open redirect","description":"nforwardauth is a forward auth service that allows the use of a single authentication middleware for multiple sites. Versions prior to 1.5.1 accept an unvalidated `r` query parameter on the `/login` endpoint and use them as the post-authentication redirect destination. An unauthenticated attacker can create a legitimate `nforwardauth` login URL that redirects a victim to an attacker-controlled website after the victim successfully authenticates. This issue may facilitate phishing and other social-engineering attacks by abusing the trust associated with the legitimate authentication domain. This vulnerability does not provide an unauthenticated ForwardAuth bypass. Version 1.5.1 contains a patch.","status":"published","published":"2026-10-26T17:19:15.467Z","modified":"2026-10-26T19:34:58.155Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-601"],"updated_at":"2026-11-02T13:36:29.327819Z"}],"euvd":[{"id":"EUVD-2026-110037","description":"nforwardauth is a forward auth service that allows the use of a single authentication middleware for multiple sites. Versions prior to 1.5.1 accept an unvalidated `r` query parameter on the `/login` endpoint and use them as the post-authentication redirect destination. An unauthenticated attacker can create a legitimate `nforwardauth` login URL that redirects a victim to an attacker-controlled website after the victim successfully authenticates. This issue may facilitate phishing and other social-engineering attacks by abusing the trust associated with the legitimate authentication domain. This vulnerability does not provide an unauthenticated ForwardAuth bypass. Version 1.5.1 contains a patch.","status":"published","published":"2026-10-26T17:19:15Z","modified":"2026-10-26T19:34:58Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T16:59:28.357127Z"}],"nvd":[{"id":"CVE-2026-81509","description":"nforwardauth is a forward auth service that allows the use of a single authentication middleware for multiple sites. Versions prior to 1.5.1 accept an unvalidated `r` query parameter on the `/login` endpoint and use them as the post-authentication redirect destination. An unauthenticated attacker can create a legitimate `nforwardauth` login URL that redirects a victim to an attacker-controlled website after the victim successfully authenticates. This issue may facilitate phishing and other social-engineering attacks by abusing the trust associated with the legitimate authentication domain. This vulnerability does not provide an unauthenticated ForwardAuth bypass. Version 1.5.1 contains a patch.","status":"published","published":"2026-10-26T18:18:46.367Z","modified":"2026-10-26T20:18:37.683Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-601"],"updated_at":"2026-11-02T14:13:03.452847Z"}],"osv":[{"id":"CVE-2026-81509","title":"nforwardauth: Unvalidated r parameter allows post-authentication open redirect","description":"nforwardauth is a forward auth service that allows the use of a single authentication middleware for multiple sites. Versions prior to 1.5.1 accept an unvalidated `r` query parameter on the `/login` endpoint and use them as the post-authentication redirect destination. An unauthenticated attacker can create a legitimate `nforwardauth` login URL that redirects a victim to an attacker-controlled website after the victim successfully authenticates. This issue may facilitate phishing and other social-engineering attacks by abusing the trust associated with the legitimate authentication domain. This vulnerability does not provide an unauthenticated ForwardAuth bypass. Version 1.5.1 contains a patch.","status":"published","published":"2026-10-26T17:19:15.467Z","modified":"2026-10-28T03:01:30.359736337Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-601"],"updated_at":"2026-11-02T15:45:18.131258Z"}]}}