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Apache HTTP Server Improper Escaping of Output Vulnerability

Exploited · KEV 2025-05-01CVE-2024-38475CWE-116

Exploited since 2025-05-01. 2 of 8 rule sources name it; Cloudflare blocks by default. Our CRS test: not blocked.

Edge rules
2/8
Our test
Not blocked
CVSS
9.1
EPSS
100.0% Top 0.1%
Posts, 14d
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Published
2024-07-01
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… More

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.

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Severity, decoded

CVSS 3.1
Critical · 9.1 / 10

Exploitable over the network, with no privileges and no user interaction, leading to full loss of confidentiality and integrity.

Over the internetNo login neededNo user actionWorks reliablySerious impact
How the score is built8 metrics
  • Attack vectorAn attacker can reach it over the internet; no access to your network needed.
    Network
  • Attack complexityNo special conditions are needed; the attack works reliably.
    Low
  • Privileges requiredNo account or login is needed.
    None
  • User interactionNo one has to click or open anything; the attack works on its own.
    None
  • ScopeThe damage stays within the vulnerable component.
    Unchanged
  • Confidentiality impactAn attacker can read all data the affected component holds, or the most sensitive parts of it.
    High
  • Integrity impactAn attacker can change any data or files the affected component protects.
    High
  • Availability impactThe component keeps working normally.
    None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CISA's assessmentSSVC, from the CVE record
ExploitationActive

Attackers are exploiting this in the wild.

AutomatableYes

Attackers can script the attack end to end and hit many targets at once.

Technical impactTotal

A successful attack gives full control over the affected software or all of its data.

Public exploits

1 found
0 Metasploit0 Exploit-DB1 Scanner template0 GitHub PoCs

Links are to third-party code: never run it outside an isolated lab.

Timeline

  1. 2024-07-01
    CVE published
    CVE List
  2. 2024-09-17
    F5 ships a rule
    Apache mod_rewrite Filename Confusion
  3. 2025-05-01
    Added to CISA KEV
    Confirmed exploitation in the wild
  4. 2025-05-19
    Cloudflare ships a rule
    Apache HTTP Server - Information Disclosure - CVE:CVE-2024-38475
  5. 2026-11-02
    Our test: OWASP Core Rule Set let it through
    paranoia level 1, anomaly threshold 5, default CRS settings
  6. 2026-11-02
    Our test: OWASP Core Rule Set let it through
    paranoia level 2, anomaly threshold 5, default CRS settings

Social

2026-10-20: 0 posts2026-10-21: 0 posts2026-10-22: 0 posts2026-10-23: 0 posts2026-10-24: 0 posts2026-10-25: 0 posts2026-10-26: 0 posts2026-10-27: 0 posts2026-10-28: 0 posts2026-10-29: 0 posts2026-10-30: 0 posts2026-10-31: 0 posts2026-11-01: 0 posts2026-11-02: 0 posts

No posts seen yet on X, Bluesky, Mastodon, Hacker News or GitHub.

Vendor statements

Quoted
CloudflareWAF Managed Rules1 quoteBlocks by default

First rule 2025-05-19, 322 days after the CVE was published.

2025-05-19New rule…75129820Default: BlockSource
Apache HTTP Server - Information Disclosure - CVE:CVE-2024-38475. Previous action: Log. New action: Block. This is a New Detection
AWSAWS WAF Managed RulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. AWS often describes a vulnerability without naming its CVE (for example "Log4j"). We count only entries that name the CVE, so AWS coverage is understated.

Microsoft AzureFront Door and Application Gateway WAF (DRS)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. The rule tables name CVEs but carry no dates, so Azure is left out of every time-to-rule figure.

Google CloudCloud Armor preconfigured WAF rulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. Google names few CVEs: the release notes start in May 2024 and the rules reference lists CVEs without dates. Its cve-canary rules are opt-in.

FastlyNext-Gen WAF virtual patchesBefore feed history

The CVE predates the oldest entry in this vendor's public feed, so a rule may exist that we cannot see.

F5Attack signatures (Distributed Cloud WAF)2 quotesRule published

First rule 2024-09-17, 78 days after the CVE was published.

2024-09-17New rule200007072Source
Added: signature 200007072 "Apache mod_rewrite Filename Confusion" (Path Traversal, risk Low), systems: Apache. References: CVE-2024-39573, CVE-2024-38475, CVE-2024-38474, CVE-2024-38476.
2025-04-28Updated200007072Source
Updated: signature 200007072 "Apache mod_rewrite Filename Confusion" (Path Traversal, risk Low), systems: Apache. References: CVE-2024-39573, CVE-2024-38475, CVE-2024-38474, CVE-2024-38476, CVE-2024-38473.
AkamaiApp & API Protector (Adaptive Security Engine)No public source

This vendor publishes no machine-readable rule changelog we can check.

OWASP CRSCore Rule Set (open source, used inside many WAFs)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. CRS rarely names CVEs: it relies on generic detections. Our own lab measures what it actually blocks.