CVE-2026-81509 nforwardauth: Unvalidated r parameter allows post-authentication open redirect
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-81509?
CVE-2026-81509 is a medium-severity vulnerability in nosduco nforwardauth, published on 26 Oct 2026.
Official 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.
Weakness: CWE-601
Which versions are affected by CVE-2026-81509?
How do I fix CVE-2026-81509?
No fix has been published for CVE-2026-81509 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-81509 being exploited?
There is no known exploitation of CVE-2026-81509 in the wild and no public exploit code.
Sources
Also known as GHSA-q64r-v7j5-6hfg.