# CVE-2024-38475: Apache HTTP Server Improper Escaping of Output Vulnerability

- Exploited (CISA KEV): yes, added 2025-05-01
- Published: 2024-07-01
- CVSS: 9.1 CRITICAL (v3.1)
- EPSS: 100.0% (100th percentile)
- CWE: CWE-116

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.

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Blocks by default | 2025-05-19 | 322 |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | No public claim | — | — |
| Fastly | Before feed history | — | — |
| F5 | Rule published | 2024-09-17 | 78 |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

### Cloudflare

- 2025-05-19 · new · rule 5c3559ad62994e5b932d7d0075129820 · default Block
  > Apache HTTP Server - Information Disclosure - CVE:CVE-2024-38475. Previous action: Log. New action: Block. This is a New Detection
  Source: https://developers.cloudflare.com/changelog/post/2025-05-19-waf-release/

### F5

- 2024-09-17 · new · rule 200007072
  > 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.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog
- 2025-04-28 · updated · rule 200007072
  > 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.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog
- 2025-05-22 · updated · rule 200007072
  > 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.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog

## Our test (measured)

- OWASP Core Rule Set 4.25.0, paranoia level 1, anomaly threshold 5, default CRS settings: passed (0 of 2 requests blocked), template CVE-2024-38475, 2026-11-02
- OWASP Core Rule Set 4.25.0, paranoia level 2, anomaly threshold 5, default CRS settings: passed (0 of 2 requests blocked), template CVE-2024-38475, 2026-11-02

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2024-38475 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2024-38475