oauth2-proxy: Improper Neutralization of HTTP Headers for Scripting Syntax
CVE-2025-64484 is a high-severity improper neutralization of HTTP headers for scripting syntax vulnerability in oauth2-proxy, with a CVSS 3.1 base score of 8.5 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected oauth2-proxy versions: < 7.13.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.66% chance of exploitation within 30 days, higher than 52% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of oauth2-proxy you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Oauth2-proxy | oauth2-proxy | < 7.13.0 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N. Scored by CNA (github.com).
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of HTTP Headers for Scripting Syntax
The product does not neutralize or incorrectly neutralizes web scripting syntax in HTTP headers that can be used by web browser components that can process raw headers, such as Flash.
How developers prevent this class of flaw
- Carefully control data that is being placed both in HTTP response headers and in the HTTP response body to ensure that no scripting syntax is present, taking various encodings into account. Perform output validation in order to filter/escape/encode unsafe data that is being passed from the server in an HTTP response header.
- Disable script execution functionality in the clients' browser.
More Improper Neutralization of HTTP Headers for Scripting Syntax vulnerabilities (CWE-644)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in oauth2-proxy
- 9.1 Critical severity
- 8.2 High severity
- 9.1 Critical severity
- 9.1 Critical severity
- 9.1 Critical severity
Recent Improper Neutralization of HTTP Headers for Scripting Syntax vulnerabilities
- 7.5 High severity
- 8.8 High severity
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