OAuth2-Proxy vulnerable to header smuggling via underscore, leading to potential privilege escalation
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- High · Low · None
- Fix status
- Partial Red Hat: 1 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat.
Summary
OAuth2-Proxy is an open-source tool that can act as either a standalone reverse proxy or a middleware component integrated into existing reverse proxy or load balancer setups. In versions prior to 7.13.0, 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. 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 `X_Forwarded-for` will now be treated as equivalent and stripped away. For those who have a rational that requires keeping a similar looking header and not stripping it, the maintainers introduced a new configuration field for Headers managed through the AlphaConfig called `InsecureSkipHeaderNormalization`. As a workaround, ensure filtering and processing logic in upstream services don't treat underscores and hyphens in Headers the same way.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| oauth2-proxy | oauth2-proxy | before 7.13.0 | 7.13.0 | Patch available | CNA |
| — | github.com/oauth2-proxy/oauth2-proxy/v7 (Go) | before 7.13.0 | 7.13.0 | Patch available | GHSA-vjrc-mh2v-45x6 |
- oauth2-proxy Vendoroauth2-proxy Affected before 7.13.0 Fixed in 7.13.0 Patch available CNA
- github.com/oauth2-proxy/oauth2-proxy/v7 (Go) Vendor— Affected before 7.13.0 Fixed in 7.13.0 Patch available GHSA-vjrc-mh2v-45x6
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:*:*:* | — | — | oauth2-proxy |
- cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:*:*:* Versions — — ·oauth2-proxy
Remediation
- Fix · CNA oauth2-proxy (oauth2-proxy) Fixed in 7.13.0
- Fix · GHSA-vjrc-mh2v-45x6 github.com/oauth2-proxy/oauth2-proxy/v7 (Go) Fixed in 7.13.0 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Ceph Storage 8 | Affected | No fix yet |
Timeline
- 2026-10-02 Threatist record created from CVE-2025-64484
- 2026-10-03 Alias added: GHSA-vjrc-mh2v-45x6
- 2026-10-11 EPSS moved to the 50th–90th percentile
References
Other 8
- https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-vjrc-mh2v-45x6
- https://datatracker.ietf.org/doc/html/rfc2616#section-4.2
- https://datatracker.ietf.org/doc/html/rfc822#section-3.2
- https://github.security.telekom.com/2020/05/smuggling-http-headers-through-reverse-proxies.html
- https://www.uptimia.com/questions/why-are-http-headers-with-underscores-dropped-by-nginx
- https://github.com/oauth2-proxy/oauth2-proxy/commit/f3f30fa976fb4bb97d6345ba4735cb6d86e24f95
- https://github.com/oauth2-proxy/oauth2-proxy
- https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.13.0
More oauth2-proxy vulnerabilities
- TI-2026-53671 OAuth2 Proxy 7.15.2 through 7.15.4 Authentication Bypass via X-Forwarded-Uri Under the Default Trusted Proxy Set CVSS 4.0CRITICAL 9.3
- TI-2025-34353 OAuth2-Proxy has authentication bypass in oauth2-proxy skip_auth_routes due to Query Parameter inclusion CVSS 3.1CRITICAL 9.1
- TI-2026-29315 OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing CVSS 3.1CRITICAL 9.1
- TI-2026-26722 OAuth2 Proxy: Health Check User-Agent Matching Bypasses Authentication in auth_request Mode CVSS 3.1CRITICAL 9.1
- TI-2026-29698 OAuth2 Proxy has an Authentication Bypass via Fragment Confusion in skip_auth_routes and skip_auth_regex CVSS 3.1HIGH 8.2
- TI-2017-14408 CSRF in Bitly oauth2_proxy 2.1 during authentication flow CVSS 3.0HIGH 8.8
Sources
- CVE-2025-64484 · CVE Program
- CVE-2025-64484 · NVD
- FIRST EPSS
- GHSA-vjrc-mh2v-45x6 · GitHub Advisory Database · CC BY 4.0
- CVE-2025-64484 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences