---
title: "CVE-2026-40575: OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing"
url: https://erroneo.us/security/cve/CVE-2026-40575/
description: "CVE-2026-40575 (github.com/oauth2-proxy/oauth2-proxy/v7 (Go)): OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-04-21
date_modified: 2026-07-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-40575"
kev: false
cvss: 9.1
epss: 0.00732
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-40575: OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.7% , percentile 54: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 54% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes github.com/oauth2-proxy/oauth2-proxy/v7 (Go) >= 7.5.0, < 7.15.2, fixed in 7.15.2 . Check your lockfile, including transitive dependencies.

## What it is

OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 may trust a client-supplied X-Forwarded-Uri header when --reverse-proxy is enabled and --skip-auth-regex or --skip-auth-route is configured. An attacker can spoof this header so OAuth2 Proxy evaluates authentication and skip-auth rules against a different path than the one actually sent to the upstream application. This can result in an unauthenticated remote attacker bypassing authentication and accessing protected routes without a valid session. Impacted users are deployments that run oauth2-proxy with --reverse-proxy enabled and configure at least one --skip-auth-regex or --skip-auth-route rule. This issue is patched in v7.15.2. Some workarounds are available for those who cannot upgrade immediately. Strip any client-provided X-Forwarded-Uri header at the reverse proxy or load balancer level; explicitly overwrite X-Forwarded-Uri with the actual request URI before forwarding requests to OAuth2 Proxy; restrict direct client access to OAuth2 Proxy so it can only be reached through a trusted reverse proxy; and/or remove or narrow --skip-auth-regex / --skip-auth-route rules where possible. For nginx-based deployments, ensure X-Forwarded-Uri is set by nginx and not passed through from the client.

## Affected packages

- Go `github.com/oauth2-proxy/oauth2-proxy/v7` >= 7.5.0, < 7.15.2 → fixed: 7.15.2

## Affected products (CVE record)

- oauth2-proxy oauth2-proxy: >= 7.5.0, < 7.15.2

## Severity

- GitHub_M CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`
- redhat-SADP CVSS 3.1: 8.7 `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N`
- GitHub CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.73% probability of exploitation activity in the next 30 days; percentile 54.

## Sources

- [GitHub Advisory GHSA-7x63-xv5r-3p2x](https://github.com/advisories/GHSA-7x63-xv5r-3p2x)
- [CVE.org record CVE-2026-40575](https://www.cve.org/CVERecord?id=CVE-2026-40575)
- [NVD entry CVE-2026-40575](https://nvd.nist.gov/vuln/detail/CVE-2026-40575)
- [github.com](https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-7x63-xv5r-3p2x)
- [access.redhat.com](https://access.redhat.com/security/cve/CVE-2026-40575)
- [RHBZ#2460449](https://bugzilla.redhat.com/show_bug.cgi?id=2460449)
- [security.access.redhat.com](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40575.json)

---
Source page: https://erroneo.us/security/cve/CVE-2026-40575/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt