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Fencer Intel
high 8.5

CVE-2025-64484 json

OAuth2-Proxy vulnerable to header smuggling via underscore, leading to potential privilege escalation

published 11mo ago modified 4mo ago also BIT-oauth2-proxy-2025-64484 , EUVD-2025-50825 , GHSA-vjrc-mh2v-45x6 , GO-2025-4113

cvss
8.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 51%
public exploits
0
none known

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.

Patch / fix

  • go github.com/oauth2-proxy/oauth2-proxy/v7 7.13.0
  • bitnami oauth2-proxy 7.13.0
  • oauth2_proxy_project oauth2_proxy 7.13.0
  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-64484 updated cvss 8.5

oauth2-proxy: OAuth2-Proxy vulnerable to header smuggling via underscore, leading to potential privilege escalation

  • Red Hat Ceph Storage 8 rhceph/oauth2-proxy-rhel9
    affected: workaround, no fix available “No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
11mo ago

Exploit prediction

0.66% chance of exploitation in the next 30 days, higher than 51% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 8.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
GitHub 3.1 8.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
OSV 3.1 8.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N

Affected packages

ecosystem package affected fixed in
go github.com/oauth2-proxy/oauth2-proxy/v7
<7.13.0
7.13.0
bitnami oauth2-proxy
<7.13.0
7.13.0
go github.com/oauth2-proxy/oauth2-proxy
all versions
 no fix listed

Affected products

  • oauth2-proxy oauth2-proxy

Classification

Weakness
  • CWE-644 Improper Neutralization of HTTP Headers for Scripting Syntax

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.