Analysis Summary

Apache Traffic Server (ATS), a widely used high-performance HTTP proxy server, has been found vulnerable to a request smuggling attack, tracked as CVE-2024-53868. This flaw arises from how ATS processes chunked transfer encoding, potentially allowing attackers to manipulate HTTP request handling. Originally a commercial product, ATS was later donated to the Apache Foundation and is now a crucial part of many Content Delivery Networks (CDNs). It supports both HTTP/1.1 and HTTP/2, making it a popular choice for high-speed web traffic management.

The vulnerability stems from improper parsing of chunked messages, which attackers can exploit to “smuggle” hidden HTTP requests within legitimate ones. Request smuggling can have severe security implications, including bypassing security controls such as web application firewalls, cache poisoning where malicious requests are stored and served to other users, and session hijacking that enables attackers to manipulate user sessions. This vulnerability affects ATS versions 9.0.0 to 9.2.9 and 10.0.0 to 10.0.4.

To protect against this flaw, immediate updates are recommended. Users running ATS on the 9.x branch should upgrade to version 9.2.10 or later, while those on the 10.x branch should upgrade to 10.0.5 or later. Keeping ATS up to date is critical to preventing exploitation and ensuring secure HTTP traffic management.

Impact

• Gain Access
• Security Bypass

Indicators of Compromise

CVE

• CVE-2024-53868

Affected Vendor

Apache

Affected Products

• Apache Traffic Server ATS 9.0.0 to 9.2.9
• Apache Traffic Server ATS 10.0.0 to 10.0.4

Remediation

• Update ATS to 9.2.10+ (9.x) or 10.0.5+ (10.x) to patch CVE-2024-53868.
• Enforce strict request validation to reject malformed chunked encoding.
• Enable header normalization to prevent inconsistencies in HTTP parsing.
• Use a WAF with request smuggling detection and filtering.
• Implement rate limiting and anomaly detection to block suspicious traffic.
• Monitor logs and request headers for unusual behavior.
• Deploy IDS/IPS systems to flag potential exploitation attempts.
• Restrict untrusted inputs and disable HTTP/1.1 pipelining if unnecessary.
• Segment ATS from sensitive systems to limit attack impact.
• Adopt zero-trust security principles for stricter access control.