What happened

CISA added CVE-2024-38475 to the Known Exploited Vulnerabilities catalog, confirming in-the-wild exploitation of Apache HTTP Server’s mod_rewrite flaw CISA KEV. The issue is an improper escaping/neutralization bug (CWE-116) allowing crafted URLs to map to filesystem locations that are permitted by the server but not intentionally reachable, enabling code execution or source code disclosure NVD entry. The KEV entry sets a remediation due date of 2025-05-22 with the required action to apply vendor mitigations or discontinue use if unavailable CISA KEV.

The CVE record tracks the weakness in Apache HTTP Server’s URL rewriting module, implicating rule-processing and output escaping behavior in unintended path exposure MITRE CVE record. Both the CISA and NVD descriptions align: attacker-controlled URLs can be rewritten to files that the server is allowed to serve but that were not intended to be directly reachable, with possible RCE or source leakage NVD entry.

Why it matters

Apache HTTP Server underpins a large fraction of public and internal web services, and mod_rewrite is frequently enabled to shape application routing and access paths NVD entry. A flaw that lets an external URL resolve to unlinked or hidden files collapses trust boundaries between URL space and the filesystem, creating direct pathways to sensitive code paths MITRE CVE record. Because the vulnerability can lead to remote code execution or disclosure of source code, compromise scenarios include application takeover and leakage of proprietary logic or secrets embedded in source files CISA KEV.

Inclusion in CISA’s KEV means active exploitation has been observed by credible sources and remediation is mandatory for U.S. Federal Civilian Executive Branch under BOD 22-01 timelines CISA KEV. CWE-116 classifies this as improper output encoding/escaping, which often manifests as data crossing a trust boundary without correct neutralization—here, the URL-to-filesystem mapping path NVD entry. When rewrite rules mis-handle escaping, “security through obscurity” paths stop being obscure and become trivially reachable by a hostile request stream MITRE CVE record.

Technical detail

mod_rewrite processes inbound URLs via ordered rules that can translate request paths into internal filesystem locations or handlers, and flaws in escaping let crafted inputs steer to unintended targets NVD entry. The vulnerability allows a client to map a URL to a location that httpd is configured to serve but which has no explicit, intended URL, eroding assumptions that “unlinked” means “unreachable” CISA KEV. In such conditions, rewritten requests can hit executable code paths or expose raw source depending on server configuration, satisfying the impact described for this CVE NVD entry.

This weakness is tracked under CWE-116, reflecting improper escaping/neutralization during output handling that enables cross-boundary effects from URLs into the httpd content space NVD entry. CISA’s listing indicates the issue is being exploited, so assumptions that obscure paths or indirect routing are sufficient controls are invalid against real adversary behavior CISA KEV. The authoritative CVE record mirrors these mechanics without prescribing specific versions or configurations, signaling defenders should focus on vendor guidance and configuration review rather than speculation MITRE CVE record.

Defense

Apply mitigations per vendor instructions and follow BOD 22-01 for cloud services or discontinue affected instances if mitigations are unavailable, aligned with the KEV directive and due date CISA KEV. Track this CVE via NVD and vendor bulletins for updates on patches or hardening steps as they publish NVD entry. Reference the CVE record to align internal tickets and inventories across teams using a consistent identifier during remediation MITRE CVE record.

Hardening and detection guidance:

• Inventory where Apache HTTP Server is exposed and where mod_rewrite is active, prioritizing internet-facing hosts for immediate review and mitigation NVD entry.
• Audit rewrite rules for transformations that reach into sensitive directories or handlers that should never be invoked by untrusted URLs, and test negative cases explicitly MITRE CVE record.
• Monitor access logs for sudden 200/304 hits on paths that have no links in the app (e.g., internal-only routes or source file paths), especially following high-rate 404/403 probing CISA KEV.
• Correlate request URLs with resolved filesystem targets to catch mismatches where the apparent path would never map to the served file in a safe configuration NVD entry.
• Alert on httpd processes unexpectedly executing interpreters or handlers for content types that should be static-only in a given vhost, as this may reflect rewritten access into executable paths NVD entry.

For federal programs and contractors, align remediation tracking with the KEV due date and BOD 22-01 compliance reporting, using the KEV reference as the authoritative trigger CISA KEV.

Lyrie Verdict

Rewrite-driven reachability bugs are ideal for autonomous attackers that can iterate URL patterns until a rewrite resolves to a sensitive path, and KEV inclusion confirms real-world abuse pressure exists now CISA KEV. Lyrie binds HTTP request/response telemetry with filesystem and process events to surface “impossible” URL→file mappings in near-real time, keyed to CVE-2024-38475 semantics for Apache httpd NVD entry. We detect machine-speed fuzzing sequences against rewrite boundaries followed by rare 200s on non-routable files and unexpected interpreter spawns from httpd, then auto-promote those chains for containment before human triage can start MITRE CVE record. This is the class of web-layer abuse our anti-rogue-AI stack is built to catch—autonomously—when the attacker’s only advantage is iteration speed and probabilistic discovery of mis-escaped rewrite paths CISA KEV.