OAuth2-Proxy is vulnerable to header smuggling via underscore leading to potential privilege escalation

Exploitation

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

CVSS

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

EPSS

• CVE-2025-64484: 0.66% estimated exploitation activity in the next 30 days; percentile 51.54 (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 All deployments of OAuth2 Proxy in front of applications that normalize underscores to dashes in HTTP headers (e.g., WSGI-based frameworks such as Django, Flask, FastAPI, and PHP applications). Authenticated users can inject underscore variants of X-Forwarded- headers that bypass the proxy’s filtering logic, potentially escalating privileges in the upstream app. OAuth2 Proxy authentication/authorization itself is not compromised. Patches This change mitigates a request header smuggling vulnerability where an attacker could bypass header stripping by using different capitalization or replacing dashes with underscores. The problem has been patched with v7.13.0. By default all specified headers will now be normalized, meaning that both capitalization and the use of underscores () versus dashes (-) will be ignored when matching headers to be stripped. For example, both X-Forwarded-For and XForwarded-for will now be treated as equivalent and stripped away. However, if users have a…

Published by the source

12 Nov 2025, 21:42 UTC

Last modified by the source

12 Nov 2025, 21:42 UTC

Source last checked

26 Oct 2026, 15:13 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-vjrc-mh2v-45x6

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# Patch Next advisory brief: CVE-2025-64484

Advisory: OAuth2-Proxy is vulnerable to header smuggling via underscore leading to potential privilege escalation
IDs: CVE-2025-64484, GHSA-vjrc-mh2v-45x6
Record: https://patchnext.com/advisories/cve-2025-64484 (revision 1, source checked 26 Oct 2026, 15:13 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.5)
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 7.13.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/oauth2-proxy/oauth2-proxy/v7: affected < 7.13.0; fixed in 7.13.0

## 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-vjrc-mh2v-45x6 (GitHub-reviewed advisory GHSA-vjrc-mh2v-45x6 lists affected ranges: Go github.com/oauth2-proxy/oauth2-proxy/v7 >=0 <7.13.0)

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