CVE-2024-38475 BIT-apache-2024-38475
Apache HTTP Server weakness in mod_rewrite when first segment of substitution matches filesystem path.
Critical
Known exploited
- Severity
- 9.1 / 10
- Critical · CVSS 3.1
- Exploit chance (EPSS)
- 99.96%
- Chance of exploitation in the next 30 days. Higher than 99.98% of scored vulnerabilities.
- Known exploited
- Yes
- In CISA's catalog since May 1, 2025
- Weakness
- CWE-116 Improper Encoding or Escaping of Output
- Fix
- None yet
- No fixed version published
Exploited in the wild. Apache HTTP Server Improper Escaping of Output Vulnerability (Apache HTTP Server). 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. Due for U.S. federal agencies by May 22, 2025.
Description
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.
How to fix
No fixed version has been published yet. Until one is, remove or replace the package, or turn off or isolate the affected feature. This page updates when a fix ships.
Severity breakdown
CVSS 3.1 9.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Weakness
CWE-116: Improper Encoding or Escaping of Output
The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.
How to prevent it
- Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using the ESAPI Encoding control [REF-45] or a similar tool, library, or framework. These will help the programmer encode outputs in a manner less prone to error. Alternately, use built-in functions, but consider using wrappers in case those functions are discovered to have a vulnerability.
- Architecture and Design: If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated. For example, stored procedures can enforce database query structure and reduce the likelihood of SQL injection.
- Architecture and Design, Implementation: Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages. Study all expected communication protocols and data representations to determine the required encoding strategies.
- Architecture and Design: In some cases, input validation may be an important strategy when output encoding is not a complete solution. For example, you may be providing the same output that will be processed by multiple consumers that use different encodings or representations. In other cases, you may be required to allow user-supplied input to contain control information, such as limited HTML tags that support formatting in a wiki or bulletin board. When this type of requirement must be met, use an extremely strict allowlist to limit which control sequences can be used. Verify that the resulting syntactic structure is what you expect. Use your normal encoding methods for the remainder of the input.
- Architecture and Design: Use input validation as a defense-in-depth measure to reduce the likelihood of output encoding errors (see CWE-20).
- Requirements: Fully specify which encodings are required by components that will be communicating with each other.
- Implementation: When exchanging data between components, ensure that both components are using the same character encoding. Ensure that the proper encoding is applied at each interface. Explicitly set the encoding you are using whenever the protocol allows you to do so.
References
Advisories
Fixes and patches
Other links
Timeline
- Published
- Added to CISA's Known Exploited Vulnerabilities catalog
- Remediation due for U.S. federal agencies
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-qxg6-89mg-rqv8 Vitest: Code injection via unauthenticated manual mock registration | Medium | Same weakness, CWE-116 |
| GHSA-333x-w4r6-6crp fast-uri vulnerable to scheme injection via an unescaped first-segment colon in suffix references | Low | Same weakness, CWE-116 |
| GHSA-xw65-4hp5-5hc7 Handlebars: JavaScript Injection via Unsafe Inline Embedding of Precompiled Templates | Medium | Same weakness, CWE-116 |
| GHSA-wx4j-mvgx-mqwp Satori-generated SVG has improper escaping | Medium | Same weakness, CWE-116 |
| GHSA-7c7c-373r-gfjj Klever-Go: Elasticsearch bulk / painless injection via on-chain account name -> explorer/indexer data forgery | High | Same weakness, CWE-116 |
| EEF-CVE-2026-82756 ash_authentication_oauth2_server interpolates a tenant-derived value into the WWW-Authenticate challenge without escaping, allowing header parameter injection | Not rated yet | Same weakness, CWE-116 |
| GHSA-qw65-cvwx-89v3 fast-uri vulnerable to authority injection via an unvalidated port in serialize | High | Same weakness, CWE-116 |
| GHSA-6gmq-8vp8-gcm6 xmldom: XML fragment injection via invalid EntityReference.nodeName during requireWellFormed serialization | Medium | Same weakness, CWE-116 |
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