CVE-2025-65114: 
Apache Traffic Server vulnerability analysis and mitigation

CVE-2025-65114 is an HTTP Request Smuggling vulnerability in Apache Traffic Server (ATS) caused by improper handling of malformed chunked transfer-encoding messages. It affects Apache Traffic Server versions 9.0.0 through 9.2.12 and 10.0.0 through 10.1.1. The vulnerability was published on April 2, 2026, with patches available in versions 9.2.13 and 10.1.2. It carries a CVSS v3.1 base score of 7.5 (High) (GitHub Advisory, Apache Mailing List).

The root cause is classified as CWE-444 (Inconsistent Interpretation of HTTP Requests / HTTP Request Smuggling), where Apache Traffic Server, acting as an intermediary proxy, fails to consistently parse malformed chunked HTTP messages relative to how downstream servers interpret them. An unauthenticated remote attacker can craft HTTP requests with malformed Transfer-Encoding: chunked bodies that are parsed differently by ATS and the backend server, enabling request smuggling. No authentication or user interaction is required, and the attack complexity is low, making it accessible to a broad range of threat actors (GitHub Advisory, Apache Mailing List).

Successful exploitation can allow attackers to bypass security controls enforced by Apache Traffic Server, inject malicious requests into backend systems, poison HTTP caches, hijack user sessions, or gain unauthorized access to sensitive data. The integrity impact is rated High with no direct confidentiality or availability impact per the CVSS score, though secondary effects such as cache poisoning or session hijacking can lead to significant data exposure. Organizations using ATS as a reverse proxy or CDN edge layer face the greatest risk, as smuggled requests could affect all users routed through the affected instance (GitHub Advisory).

1. Reconnaissance: Identify internet-facing Apache Traffic Server instances running versions 9.0.0–9.2.12 or 10.0.0–10.1.1 using tools like Shodan, Censys, or HTTP banner analysis.
2. Craft malformed chunked request: Construct an HTTP request with a malformed Transfer-Encoding: chunked body — for example, using ambiguous chunk sizes, invalid chunk terminators, or conflicting Content-Length and Transfer-Encoding headers — designed to be interpreted differently by ATS and the backend server.
3. Send smuggled request: Transmit the crafted request to the ATS proxy. ATS processes the outer request and forwards what it believes is a complete request to the backend, while the malformed chunked body causes the backend to interpret the remainder as the beginning of a new, attacker-controlled request.
4. Achieve objective: The smuggled request prefix is prepended to the next legitimate user's request on the backend, potentially allowing the attacker to hijack sessions, poison caches, bypass access controls, or inject malicious content into responses (GitHub Advisory, Apache Mailing List).

• Network: Unusual HTTP requests to ATS with both Transfer-Encoding: chunked and Content-Length headers present simultaneously; requests with malformed or non-standard chunk size values; unexpected HTTP 400/500 responses from backend servers following seemingly normal ATS-proxied requests.
• Logs: ATS access logs showing requests with anomalous Transfer-Encoding header values or oversized/malformed chunked bodies; backend server logs recording requests that do not correspond to any client-initiated session; unexpected cache entries or cache poisoning artifacts in ATS cache logs.
• Process/Behavior: Unexplained session crossover events where one user receives another user's response; backend applications logging requests with unexpected headers or paths not initiated by legitimate clients.

Apache has released patched versions addressing this vulnerability: upgrade to 9.2.13 (for the 9.x branch) or 10.1.2 (for the 10.x branch). Organizations unable to patch immediately should implement network-level request validation to detect and block malformed chunked HTTP messages, and monitor for anomalous Transfer-Encoding header patterns. Restricting direct internet exposure of ATS instances and placing a strict HTTP parser in front of ATS can reduce risk as a temporary measure (GitHub Advisory, Apache Mailing List).

Security news outlets including GBHackers, CyberSecurityNews, and CyberPress covered the vulnerability shortly after disclosure, framing it alongside related ATS DoS vulnerabilities patched in the same release cycle. The Hacker Wire noted the issue on Mastodon, and Debian and Fedora Linux distributions issued updated packages for their trafficserver packages. Community reaction has been measured, with no major threat actor attribution or widespread alarm, consistent with the absence of active exploitation (GBHackers, SecurityOnline).