Apache HTTP Server Improper Escaping of Output Vulnerability
Improper escaping of output in mod_rewrite in Apache HTTP Server 2.4.59 and earlier allows an attacker to map URLs to filesystem locations that are permitted to be served by the server but are not intentionally/directly reachable by any URL, resulting in code execution or source code disclosure. Substitutions in server context that use a backreferences or variables as the first segment of the su
What happened
Improper escaping of output in mod_rewrite in Apache HTTP Server 2.4.59 and earlier allows an attacker to map URLs to filesystem locations that are permitted to be served by the server but are not intentionally/directly reachable by any URL, resulting in code execution or source code disclosure. Substitutions in server context that use a backreferences or variables as the first segment of the substitution are affected. Some unsafe RewiteRules will be broken by this change and the rewrite flag "UnsafePrefixStat" can be used to opt back in once ensuring the substitution is appropriately constrained.
CISA lists it as exploited, added 01 May 2025.
Does it affect you
Names Apache HTTP Server. Enter the product and version you run to place it against the affected range the vendor published.
What to do
- Follow the vendor advisory for the fixed release and any interim mitigation.
httpd.apache.org - Apply the vendor patch named in this advisory.
github.com - Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
cisa.gov
CISA’s notes for this entry:
- This vulnerability affects a common open-source component, third-party library, or a protocol used by different products. Please check with specific vendors for information on patching status. For more information, please see: httpd.apache.org/security/vulnerabilities_24.html
- nvd.nist.gov/vuln/detail/CVE-2024-38475
Affected, as published to NVD
- httpd
- Apache HTTP Server: 2.4.0 up to the fix in 2.4.60
The record
- NVD status
- Analyzed
- Published
- 01 Jul 2024, last modified 17 Jun 2026 (NVD)
- Severity
- CVSS 3.1 base score 9.1, Critical — computed here from the vector; NVD states 9.1.
- Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- Weakness
- CWE-116 (NVD; names by MITRE)
- Exploitation
- Listed in CISA’s Known Exploited Vulnerabilities catalogue since 01 May 2025; federal remediation due 22 May 2025. CISA entry
- Exploit probability
- EPSS 100.0%, 100th percentile — FIRST, scored 23 Oct 2026. FIRST EPSS
- Vendor
- Apache · HTTP Server (CISA)
References on the NVD record
- httpd.apache.org/security/vulnerabilities_24.htmlVendor Advisory
- github.com/apache/httpd/commit/9a6157d1e2f7ab15963020381054b48782bc18cfPatch
- security.netapp.com/advisory/ntap-20240712-0001/Third Party Advisory
- openwall.com/lists/oss-security/2024/07/01/8Third Party Advisory
- psirt.global.sonicwall.com/vuln-detail/SNWLID-2024-0018Third Party Advisory
- blackhat.com/us-24/briefings/schedule/index.html#confusion-attacks-exploiting-hidden-semantic-ambiguity-in-apache-http-server-pre-recorded-40227Third Party Advisory
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-38475Third Party AdvisoryUS Government Resource
Sources
The verdict above is computed from the products and versions you entered and the affected ranges the vendor published to NVD. It does not inspect your environment, and this site never reports a product as unaffected: why.