nforwardauth: Unvalidated r parameter allows post-authentication open redirect

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-81509
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-26 18:18:46 UTC
Updated2026-10-26 20:18:37 UTC
Descriptionnforwardauth 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.

Risk And Classification

Primary CVSS: v3.1 6.1 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Problem Types: CWE-601 | CWE-601 CWE-601: URL Redirection to Untrusted Site ('Open Redirect')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
3.1CNADECLARED6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nosduco Nforwardauth affected < 1.5.1 Not specified

References

ReferenceSourceLinkTags
github.com/nosduco/nforwardauth/pull/71 [email protected] github.com
github.com/nosduco/nforwardauth/releases/tag/v1.5.1 [email protected] github.com
github.com/nosduco/nforwardauth/security/advisories/GHSA-q64r-v7j5-6hfg [email protected] github.com
github.com/nosduco/nforwardauth/commit/664f2602f9e1459558d1c4c55019f6d48... [email protected] github.com
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