CVE-2025-41082 Overview
CVE-2025-41082 is an HTTP Request Smuggling vulnerability (CL.0 variant) affecting Altitude Communication Server. The vulnerability arises from inconsistent analysis of multiple HTTP requests over a single Keep-Alive connection using Content-Length headers. This inconsistency causes a desynchronization between frontend and backend server request processing, potentially enabling request hiding, cache poisoning, or security bypass attacks.
Critical Impact
Attackers can exploit this HTTP request smuggling vulnerability to bypass security controls, poison web caches, and perform request hijacking attacks against users of the Altitude Communication Server platform.
Affected Products
- Altitude Communication Server
Discovery Timeline
- 2026-01-26 - CVE-2025-41082 published to NVD
- 2026-01-26 - Last updated in NVD database
Technical Details for CVE-2025-41082
Vulnerability Analysis
This vulnerability is classified under CWE-444 (Inconsistent Interpretation of HTTP Requests), commonly referred to as HTTP Request Smuggling. The CL.0 variant specifically involves scenarios where the frontend server processes Content-Length headers differently than the backend server, or where one component ignores the Content-Length entirely while the other respects it.
In this case, when multiple HTTP requests are sent over a single persistent (Keep-Alive) connection, the Altitude Communication Server's frontend and backend components parse the Content-Length headers inconsistently. This parsing discrepancy allows an attacker to craft malicious requests that are interpreted differently by each server component, effectively "smuggling" a hidden request within what appears to be a legitimate one.
Root Cause
The root cause of this vulnerability lies in the inconsistent handling of HTTP request boundaries when processing Content-Length headers across different components of the Altitude Communication Server architecture. When a frontend proxy or load balancer interprets request boundaries differently than the backend application server, request desynchronization occurs. This architectural flaw allows attackers to inject partial requests that become prepended to subsequent legitimate user requests.
Attack Vector
The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can craft specially formed HTTP requests that exploit the Content-Length parsing discrepancy to:
- Request Hiding: Embed malicious requests within seemingly legitimate traffic to bypass security controls and WAF rules
- Cache Poisoning: Manipulate web cache entries to serve malicious content to other users
- Security Bypass: Circumvent authentication or authorization mechanisms by hijacking other users' sessions
- Request Hijacking: Capture or modify legitimate requests from other users sharing the same connection
The attack involves sending a carefully crafted HTTP request where the Content-Length value is manipulated to create ambiguity in how the request body boundaries are determined. The frontend server processes the request using one interpretation while the backend uses another, leaving partial request data in the connection buffer that affects subsequent requests.
Detection Methods for CVE-2025-41082
Indicators of Compromise
- Unusual HTTP request patterns with mismatched Content-Length headers in server logs
- Unexpected 400 Bad Request errors indicating malformed or smuggled requests
- Cache anomalies where response content does not match expected request patterns
- Connection timeout irregularities on Keep-Alive connections
Detection Strategies
- Monitor HTTP access logs for requests with suspicious Content-Length header values or discrepancies
- Implement deep packet inspection to identify malformed HTTP request boundaries
- Deploy web application firewall rules specifically designed to detect HTTP request smuggling patterns
- Analyze backend server logs for requests that appear to have been prepended with unexpected data
Monitoring Recommendations
- Enable verbose HTTP request logging on both frontend proxy and backend application servers
- Configure alerts for unusual HTTP error rates, particularly 400-series errors
- Monitor for cache hit ratio anomalies that may indicate cache poisoning attempts
- Implement connection-level monitoring to detect unusual request timing patterns on persistent connections
How to Mitigate CVE-2025-41082
Immediate Actions Required
- Disable HTTP Keep-Alive connections if operationally feasible to prevent connection-based smuggling
- Configure frontend servers to normalize all incoming HTTP requests before forwarding to backend servers
- Implement strict HTTP parsing that rejects ambiguous requests
- Apply vendor patches for Altitude Communication Server as they become available
Patch Information
Organizations should consult the INCIBE Security Notice for detailed information about available patches and remediation guidance. Contact the Altitude Communication Server vendor for specific patch versions addressing this vulnerability.
Workarounds
- Disable Keep-Alive connections by configuring Connection: close headers on all responses
- Deploy a reverse proxy with strict HTTP parsing that normalizes requests before forwarding
- Implement request validation rules that reject requests with ambiguous Content-Length values
- Enable HTTP/2 end-to-end where supported, as it uses binary framing that is not susceptible to this class of vulnerability
# Example Apache configuration to disable Keep-Alive
# Add to httpd.conf or virtual host configuration
KeepAlive Off
# Alternative: Reduce Keep-Alive timeout to minimize exposure window
KeepAlive On
KeepAliveTimeout 5
MaxKeepAliveRequests 100
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
