Apache HTTP Server mod_rewrite Improper Escaping Vulnerability
Actively exploited in the wild. Patch or mitigate immediately — don't wait for a maintenance window.
An unauthenticated attacker, remotely over the network, with no user interaction, can steal data and tamper with data.
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.
Inferred from the weakness type (CWE) and how the flaw is reached — the techniques an attacker would chain to exploit this. Real-world corroboration appears here as threat intel is folded in.
Corroborated threat activity referencing this CVE — with source and confidence, not inference.
Named threat actors and observed ATT&CK techniques appear here as intel feeds are folded in — the ATT&CK chain above stays inferred until then.
Generated by Wavense from the CVE record — an immediate mitigation and the permanent fix.
Review all mod_rewrite rules, especially those in the server context using backreferences or variables as the first segment of a substitution, to identify and disable potentially unsafe configurations. Implement strict network segmentation and Web Application Firewall (WAF) rules to filter malicious requests targeting Apache. Monitor Apache access logs for anomalous URL patterns or error messages indicating attempted exploitation.
Upgrade Apache HTTP Server to version 2.4.60 or a later patched release immediately. After upgrading, carefully review and test any existing mod_rewrite rules, as some unsafe rules may break due to the fix. If absolutely necessary, the 'UnsafePrefixStat' rewrite flag can be used to re-enable certain behaviors, but only after ensuring the substitution is rigorously constrained and secure.
An attacker can exploit improper output escaping in mod_rewrite to map URLs to unintended filesystem locations. This critical flaw allows for remote code execution or the disclosure of sensitive source code. Successful exploitation could lead to full system compromise, data breaches, and severe reputational damage.
Other CVEs affecting http server
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