Apache Traffic Server Flaw Allows Request Smuggling Attacks

A critical vulnerability has been discovered in Apache Traffic Server (ATS), an open-source caching proxy server.

Identified as CVE-2024-53868, this flaw enables attackers to exploit request smuggling via malformed chunked messages.

Users of Apache Traffic Server are urged to upgrade to secure versions of the software immediately to mitigate potential risks.

CVE-2024-53868 Details

The vulnerability was reported by Jeppe Bonde Weikop and disclosed on April 3, 2025, by the Apache Software Foundation.

The flaw specifically affects the way ATS processes chunked message bodies. If improperly formatted chunked messages are sent, attackers can leverage the situation to perform HTTP request smuggling attacks.

This type of attack manipulates the processing of web requests to bypass security controls, potentially resulting in data leaks, unauthorized access, or other malicious activities.

According to the advisory, this vulnerability impacts users running certain versions of ATS. The affected versions and their recommended upgrades are detailed below.

Affected Products

Product	Affected Versions	Recommended Upgrade
Apache Traffic Server 9.x	9.0.0 to 9.2.9	Upgrade to 9.2.10+
Apache Traffic Server 10.x	10.0.0 to 10.0.4	Upgrade to 10.0.5+

Request smuggling vulnerabilities expose web applications and their backend systems to significant threats. These include:

• Bypassing Security Measures: Attackers can bypass authentication checks, firewalls, or reverse proxies.
• Session Hijacking: By injecting malicious requests, attackers can access sessions belonging to legitimate users.
• Information Disclosure: Sensitive data such as personal identifiers, login credentials, or internal server configuration details could potentially leak.
• Downtime and System Disruption: Exploiting this flaw could render the application non-operational or cause denial-of-service attacks.

The National Vulnerability Database (NVD) has acknowledged the CVE and is currently working to assign a definitive CVSS score for assessing the severity.

Mitigation and Recommendations

The best course of action for ATS users is to upgrade to the patched versions to address the vulnerability immediately:

• Users running 9.x versions should upgrade to 9.2.10 or later.
• Users running 10.x versions should upgrade to 10.0.5 or later.

Additionally, operators are recommended to:

1. Audit their ATS configurations and logs for unusual activity or exploit attempts.
2. Regularly monitor updates from the Apache Software Foundation and CVE advisory pages.
3. Implement robust network monitoring tools to identify potential cases of HTTP request smuggling.

Administrators and security teams are reminded of the importance of timely updates to maintain secure and stable systems.

This disclosure underscores the need for proactive cybersecurity measures in modern infrastructures.

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