Apache HTTP Server Improper Escaping of Output Vulnerability (CVE-2024-38475)

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.

Published Jul 1, 2024 · Updated May 29, 2026

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Why patchRisk explained in plain English

Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data. Federal agencies are required to remediate by 2025-05-22 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Software Vulnerability (CWE-116) (CWE-116) vulnerability in Apache HTTP Server. 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. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.

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Phishing link

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Malicious file

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Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

●IT Security

●Running http server: 2.4.0 ≤ v < 2.4.60; ontap 9: -; sma 200 firmware: v < 10.2.1.14-75sv; sma 210 firmware: v < 10.2.1.14-75sv; sma 400 firmware: v < 10.2.1.14-75sv; sma 410 firmware: v < 10.2.1.14-75sv; sma 500v firmware: v < 10.2.1.14-75sv

Real-world incidentsWhat we've seen

CISA added this CVE to the Known Exploited Vulnerabilities catalog on 2025-05-01 based on evidence of active exploitation in the wild. Federal agencies required to remediate by 2025-05-22.

How to patch

Get the fix

Apply the fixed package from your vendor. The advisory lists affected versions and the exact fixed build.

↗ Vendor advisory

Manual remediation steps

Apply the Vendor Patch

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.

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