OAuth2 Proxy has an Authentication Bypass via Fragment Confusion in skip_auth_routes and skip_auth_regex

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.2 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

EPSS

• CVE-2026-41059: 0.27% estimated exploitation activity in the next 30 days; percentile 19.96 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact A configuration-dependent authentication bypass exists in OAuth2 Proxy. Deployments are affected when all of the following are true: Use of skipauthroutes or the legacy skipauthregex Use of patterns that can be widened by attacker-controlled suffixes, such as ^/foo/./bar$ causing potential exposure of /foo/secret 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. Patches A fix has been implemented to normalize request paths more conservatively before skip-auth matching so…

Published by the source

15 Apr 2026, 19:24 UTC

Last modified by the source

24 Apr 2026, 20:40 UTC

Source last checked

26 Oct 2026, 15:19 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-pxq7-h93f-9jrg

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# Patch Next advisory brief: CVE-2026-41059

Advisory: OAuth2 Proxy has an Authentication Bypass via Fragment Confusion in skip_auth_routes and skip_auth_regex
IDs: CVE-2026-41059, GHSA-pxq7-h93f-9jrg
Record: https://patchnext.com/advisories/cve-2026-41059 (revision 1, source checked 26 Oct 2026, 15:19 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/oauth2-proxy/oauth2-proxy/v7 7.15.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/oauth2-proxy/oauth2-proxy/v7: affected >= 7.5.0, < 7.15.2; fixed in 7.15.2

## Suggested inspection (read-only)
- Go github.com/oauth2-proxy/oauth2-proxy/v7: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/oauth2-proxy/oauth2-proxy/v7.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-pxq7-h93f-9jrg (GitHub-reviewed advisory GHSA-pxq7-h93f-9jrg lists affected ranges: Go github.com/oauth2-proxy/oauth2-proxy/v7 >=7.5.0 <7.15.2)

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