CVE-2025-13803: MediaCrush HTTP Header Injection Vulnerability

CVE-2025-13803 Overview

A medium-severity HTTP header injection vulnerability has been identified in MediaCrush versions 1.0.0 and 1.0.1. The vulnerability exists in the Header Handler component within the file /mediacrush/paths.py, where improper neutralization of HTTP headers allows for scripting syntax injection through manipulation of the Host header argument. This flaw enables remote attackers to launch HTTP response splitting attacks without requiring authentication.

Critical Impact

Remote attackers can exploit this vulnerability to inject malicious content through HTTP headers, potentially enabling cross-site scripting (XSS) attacks, cache poisoning, or session hijacking scenarios.

Affected Products

• MediaCrush 1.0.0
• MediaCrush 1.0.1

Discovery Timeline

• 2025-12-01 - CVE-2025-13803 published to NVD
• 2025-12-01 - Last updated in NVD database

Technical Details for CVE-2025-13803

Vulnerability Analysis

This vulnerability is classified under CWE-644 (Improper Neutralization of HTTP Headers for Scripting Syntax). The affected component fails to properly sanitize or validate the Host header before processing it, allowing attackers to inject arbitrary HTTP headers or scripting content. The CVSS 4.0 score of 6.9 (Medium) reflects the network-based attack vector with low complexity and no required privileges or user interaction.

The CVSS vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N indicates:

• Attack Vector: Network (remotely exploitable)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Impact: Low confidentiality, integrity, and availability impact

The EPSS (Exploit Prediction Scoring System) probability stands at 0.051%, placing it in the 16th percentile, indicating a relatively low likelihood of exploitation in the wild.

Root Cause

The root cause lies in the paths.py file within the MediaCrush application's Header Handler component. The application fails to implement proper input validation and output encoding when processing the Host header parameter. This allows specially crafted header values to be interpreted as script syntax or additional HTTP headers, breaking the intended protocol structure.

Attack Vector

The attack can be executed remotely over the network without requiring authentication or user interaction. An attacker can craft malicious HTTP requests with specially manipulated Host header values that exploit the improper neutralization of HTTP headers. When the vulnerable server processes these headers, the injected content can lead to:

1. HTTP Response Splitting: Injecting CRLF sequences to add arbitrary headers or body content
2. Cache Poisoning: Manipulating cached responses to serve malicious content to other users
3. Cross-Site Scripting: Injecting script content that executes in victim browsers

The vulnerability mechanism involves the application processing the Host header without adequate sanitization in the /mediacrush/paths.py file. Attackers can inject carriage return and line feed characters (CRLF - \r\n) followed by malicious headers or content. For detailed technical analysis, refer to the CVE Discovery documentation.

Detection Methods for CVE-2025-13803

Indicators of Compromise

• Unusual or malformed Host headers in HTTP request logs containing CRLF sequences (%0d%0a or \r\n)
• HTTP responses containing unexpected additional headers not set by the application
• Web application logs showing requests with encoded newline characters in header values
• Evidence of cache poisoning through inconsistent cached content

Detection Strategies

Organizations can implement the following detection strategies:

1. Web Application Firewall (WAF) Rules: Configure rules to detect and block HTTP requests containing CRLF sequences or other header injection patterns in the Host header
2. Log Analysis: Monitor web server access logs for requests with encoded special characters (%0d, %0a, %0D, %0A) in header fields
3. Intrusion Detection Systems: Deploy signatures to identify HTTP header injection attempts
4. Application-Level Monitoring: Implement request validation logging to capture malformed header submissions

SentinelOne Singularity provides comprehensive protection against web application attacks including HTTP header injection attempts through real-time behavioral analysis and threat detection capabilities.

Monitoring Recommendations

• Enable verbose logging for all HTTP request headers on MediaCrush instances
• Implement real-time alerting for requests containing suspicious header patterns
• Monitor for anomalous response sizes that may indicate successful header injection
• Review cached content periodically for signs of poisoning
• Deploy network-level monitoring to detect exploitation attempts before they reach the application

How to Mitigate CVE-2025-13803

Immediate Actions Required

• Implement strict input validation on all HTTP headers, particularly the Host header
• Deploy a Web Application Firewall (WAF) with rules to filter CRLF injection attempts
• Review and harden the /mediacrush/paths.py file to sanitize header inputs
• Consider disabling or restricting access to MediaCrush instances until a patch is available
• Enable enhanced logging to detect potential exploitation attempts

Patch Information

As of the last NVD update on 2025-12-01, no official patch has been documented. Organizations should monitor the following resources for updates:

• GitHub CVE Discovery Report
• VulDB Entry 333813

Workarounds

Until an official patch is released, organizations can implement the following workarounds:

1. Input Sanitization: Implement server-side filtering to strip or reject CRLF characters from incoming HTTP headers
2. Reverse Proxy Configuration: Use a reverse proxy (nginx, Apache) in front of MediaCrush to normalize and validate headers before they reach the application
3. Network Segmentation: Restrict network access to MediaCrush instances to trusted networks only
4. Header Validation: Implement strict validation rules for the Host header format

For nginx, consider adding header validation:

# Nginx configuration to validate Host header
if ($http_host ~* "[\r\n]") {
    return 400;
}

# Additional protection against header injection
proxy_set_header Host $host;
proxy_pass_request_headers on;

For Apache, use mod_security rules:

# Apache ModSecurity rule to block CRLF in headers
SecRule REQUEST_HEADERS "@rx [\r\n]" \
    "id:1001,phase:1,deny,status:400,msg:'CRLF Injection Attempt'"