CVE-2023-25690
Published: April 11, 2026
Official 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.
Risk Analysis
Apache HTTP Server versions 2.4.0 through 2.4.55 are vulnerable to HTTP Request Smuggling when specific mod_proxy configurations are used with RewriteRule or ProxyPassMatch. This flaw can bypass access controls, proxy unintended URLs, and lead to cache poisoning. The confirmed active exploitation, as indicated by its presence in CISA's KEV catalog, makes this a critical vulnerability.
This vulnerability is actively exploited in the wild and is included in CISA's Known Exploited Vulnerabilities catalog. It is remotely exploitable.
Update Apache HTTP Server to at least version 2.4.56. Review and adjust mod_proxy configurations, especially those involving RewriteRule or ProxyPassMatch, to avoid patterns that re-insert user-supplied request-target data using variable substitution.
Technical Analysis
CVE-2023-25690 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CISA has added CVE-2023-25690 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
Affected Vendors & Products
Exploit & PoC Resources
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2023-25690 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1