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[ CVE-2024-38475 · Published 1 Jul 2024 ]

Apache HTTP Server Improper Escaping of Output Vulnerability

Exploited · CISA KEV CVSS 9.1 EPSS 100%Fix available

[ Why it matters ]Priority signals

  • Exploited in the wild: on CISA's Known Exploited Vulnerabilities list since 2025-05-01
  • EPSS: 100% chance of exploitation in the next 30 days (higher than 100% of CVEs)
  • Critical severity: CVSS 9.1

[ Description ]Official description

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: Apache HTTP Server contains an improper escaping of output vulnerability in mod_rewrite that 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.

[ Fixes ]Fixes and patches

CISA required action (US federal deadline 22 May 2025): Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

[ References ]References