CVE-2025-64484
Vulnérabilité élevée dans oauth2-proxy (oauth2-proxy)
Description
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.
Gravité et risque d'exploitation
CVE-2025-64484 obtient un score CVSS de 8.5/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.66 %, ce qui la place devant 50.5 % des CVE référencées.
Que faire ?
- Vérifiez si oauth2-proxy (versions < 7.13.0) est présent sur votre parc.
- Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
- À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
- Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.
Références
- 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