{"cve":"CVE-2025-64484","nvd":{"published":"2025-11-10T22:15:37.490","modified":"2026-06-17T09:54:26.523","status":"Deferred","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N","score":8.5},"cwes":["CWE-644"],"references":["https://datatracker.ietf.org/doc/html/rfc2616#section-4.2","https://datatracker.ietf.org/doc/html/rfc822#section-3.2","https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-vjrc-mh2v-45x6","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"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:14:53.307938015+00:00"},"epss":{"cve":"CVE-2025-64484","score":0.00658,"percentile":0.51501,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-vjrc-mh2v-45x6","url":"https://osv.dev/vulnerability/GHSA-vjrc-mh2v-45x6","summary":"OAuth2-Proxy is vulnerable to header smuggling via underscore leading to potential privilege escalation","modified":"2025-11-17T21:48:56Z","packages":[{"ecosystem":"Go","name":"github.com/oauth2-proxy/oauth2-proxy/v7","purl":"pkg:golang/github.com/oauth2-proxy/oauth2-proxy/v7","ranges":["<7.13.0"],"fixed":["7.13.0"]}]},{"id":"GO-2025-4113","url":"https://osv.dev/vulnerability/GO-2025-4113","summary":"OAuth2-Proxy is vulnerable to header smuggling via underscore leading to potential privilege escalation in github.com/oauth2-proxy/oauth2-proxy","modified":"2026-03-03T04:57:36.731541Z","packages":[{"ecosystem":"Go","name":"github.com/oauth2-proxy/oauth2-proxy","purl":"pkg:golang/github.com/oauth2-proxy/oauth2-proxy","ranges":["all versions"],"fixed":[]},{"ecosystem":"Go","name":"github.com/oauth2-proxy/oauth2-proxy/v7","purl":"pkg:golang/github.com/oauth2-proxy/oauth2-proxy/v7","ranges":["<7.13.0"],"fixed":["7.13.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}