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.
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Fixes

Solution

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Workaround

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History

Mon, 26 Oct 2026 19:30:00 +0000

Type Values Removed Values Added
First Time appeared Nosduco
Nosduco nforwardauth
Vendors & Products Nosduco
Nosduco nforwardauth

Mon, 26 Oct 2026 18:45:00 +0000

Type Values Removed Values Added
Title Unvalidated r parameter allows post-authentication open redirect nforwardauth: Unvalidated r parameter allows post-authentication open redirect

Mon, 26 Oct 2026 17:45:00 +0000

Type Values Removed Values Added
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.
Title Unvalidated r parameter allows post-authentication open redirect
Weaknesses CWE-601
References
Metrics cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-26T19:34:58.155Z

Reserved: 2026-08-26T20:58:58.084Z

Link: CVE-2026-81509

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Deferred

Published: 2026-10-26T18:18:46.367

Modified: 2026-10-26T20:18:37.683

Link: CVE-2026-81509

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-26T19:09:04Z

Weaknesses