CVE-2024-38475

Comprehensive Technical Analysis of CVE-2024-38475

1. Vulnerability Assessment and Severity Evaluation

CVE ID: CVE-2024-38475 CISA Vulnerability Name: Apache HTTP Server Improper Escaping of Output Vulnerability CVSS Score: 9.1

The vulnerability in question pertains to the improper escaping of output in the mod_rewrite module of Apache HTTP Server versions 2.4.59 and earlier. This flaw allows an attacker to map URLs to filesystem locations that are not intentionally reachable, potentially leading to code execution or source code disclosure. The high CVSS score of 9.1 indicates a critical severity, underscoring the potential for significant impact if exploited.

2. Potential Attack Vectors and Exploitation Methods

Attack Vectors:

• URL Manipulation: An attacker can craft specific URLs that exploit the improper escaping in mod_rewrite to access unintended filesystem locations.
• Code Execution: By mapping URLs to executable files, an attacker could potentially execute arbitrary code on the server.
• Source Code Disclosure: An attacker could access sensitive source code files that are not meant to be publicly accessible, leading to further exploitation or data breaches.

Exploitation Methods:

• Crafting Malicious URLs: Attackers can create URLs that leverage the vulnerability to traverse the filesystem and access restricted files.
• Using Backreferences and Variables: Exploiting substitutions in the server context that use backreferences or variables as the first segment of the substitution.

3. Affected Systems and Software Versions

Affected Software:

• Apache HTTP Server versions 2.4.59 and earlier.

Affected Systems:

• Any system running the affected versions of Apache HTTP Server, including web servers hosting critical applications and services.

4. Recommended Mitigation Strategies

Immediate Actions:

• Patching: Upgrade to the latest version of Apache HTTP Server that includes the fix for this vulnerability.
• Configuration Changes: Use the rewrite flag UnsafePrefixStat to opt back in after ensuring the substitution is appropriately constrained.

Long-Term Strategies:

• Regular Updates: Implement a regular update and patch management process for all software components.
• Security Audits: Conduct regular security audits and vulnerability assessments to identify and mitigate potential risks.
• Monitoring: Implement robust monitoring and logging to detect and respond to suspicious activities.

5. Impact on Cybersecurity Landscape

The discovery and exploitation of this vulnerability highlight the critical importance of proper input validation and output escaping in web server configurations. The potential for code execution and source code disclosure underscores the need for vigilant security practices, especially in environments where Apache HTTP Server is widely deployed. This vulnerability serves as a reminder for organizations to prioritize timely patching and continuous security assessments.

6. Technical Details for Security Professionals

Technical Overview:

• Module Affected: mod_rewrite
• Vulnerable Component: Substitutions in server context using backreferences or variables as the first segment of the substitution.
• Mitigation Flag: UnsafePrefixStat

Example of Vulnerable Configuration:

RewriteEngine On
RewriteRule ^/(.*) /$1

Example of Mitigated Configuration:

RewriteEngine On
RewriteRule ^/(.*) /$1 [UnsafePrefixStat]

Patch Reference:

• The vulnerability has been addressed in the Apache HTTP Server repository with the commit: 9a6157d1e2f7ab15963020381054b48782bc18cf.

References:

• Apache HTTP Server Vulnerabilities
• NetApp Security Advisory
• Openwall OSS Security List
• Black Hat USA 2024 Briefings

By addressing this vulnerability promptly and comprehensively, organizations can significantly reduce the risk of exploitation and maintain the integrity and security of their web services.