---
title: "CVE-2026-34457: OAuth2 Proxy's Health Check User-Agent Matching Bypasses Authentication in auth_request Mode"
url: https://erroneo.us/security/cve/CVE-2026-34457/
description: "CVE-2026-34457 (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: 2026-04-14
date_modified: 2026-04-15
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-34457"
kev: false
cvss: 9.1
epss: 0.00656
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-34457: OAuth2 Proxy's Health Check User-Agent Matching Bypasses Authentication in auth_request Mode

**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 51: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 51% 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) < 7.15.2, fixed in 7.15.2 ; github.com/oauth2-proxy/oauth2-proxy (Go) <= 3.2.0, no fixed version listed . Check your lockfile, including transitive dependencies.

## What it is

OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions prior to 7.15.2 contain a configuration-dependent authentication bypass in deployments where OAuth2 Proxy is used with an authrequest-style integration (such as nginx authrequest) and either --ping-user-agent is set or --gcp-healthchecks is enabled. In affected configurations, OAuth2 Proxy treats any request with the configured health check User-Agent value as a successful health check regardless of the requested path, allowing an unauthenticated remote attacker to bypass authentication and access protected upstream resources. Deployments that do not use authrequest-style subrequests or that do not enable --ping-user-agent/--gcp-healthchecks are not affected. This issue is fixed in 7.15.2.

## Affected packages

- Go `github.com/oauth2-proxy/oauth2-proxy/v7` < 7.15.2 → fixed: 7.15.2
- Go `github.com/oauth2-proxy/oauth2-proxy` <= 3.2.0 → fixed: none listed

## Affected products (CVE record)

- oauth2-proxy oauth2-proxy: < 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`
- 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): 0.66% probability of exploitation activity in the next 30 days; percentile 51.

## Sources

- [GitHub Advisory GHSA-5hvv-m4w4-gf6v](https://github.com/advisories/GHSA-5hvv-m4w4-gf6v)
- [CVE.org record CVE-2026-34457](https://www.cve.org/CVERecord?id=CVE-2026-34457)
- [NVD entry CVE-2026-34457](https://nvd.nist.gov/vuln/detail/CVE-2026-34457)
- [github.com](https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-5hvv-m4w4-gf6v)
- [github.com](https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.15.2)

---
Source page: https://erroneo.us/security/cve/CVE-2026-34457/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt