CVE-2026-65100 in Traffic Server
Summary
by MITRE • 07/29/2026
Apache Traffic Server updates the HTTP/2 HPACK dynamic table before confirming the header block encoded successfully, so an encode failure leaves the encoder out of sync with the peer decoder and corrupts subsequent header blocks on the connection.
This issue affects Apache Traffic Server: from 8.0.0 through 8.1.9, from 9.0.0 through 9.2.14, from 10.0.0 through 10.1.3.
Users are recommended to upgrade to version 9.2.15 or 10.1.4, which fix the issue.
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Analysis
by VulDB Data Team • 07/29/2026
This vulnerability represents a critical synchronization flaw in Apache Traffic Server's HTTP/2 implementation that stems from improper handling of header block encoding operations within the HPACK dynamic table management system. The flaw occurs when the system updates the dynamic table prior to verifying successful encoding completion, creating a race condition where encoding failures can leave the encoder and decoder in desynchronized states. This misalignment fundamentally compromises the integrity of subsequent HTTP/2 header communications on the same connection, leading to potential data corruption and service disruption.
The technical implementation issue manifests as a failure to properly manage the HPACK compression state machine during HTTP/2 header processing. When an encoding operation fails, the system continues to update the dynamic table entries that should only be modified upon successful completion of the encoding process. This violates fundamental principles of state management in protocol implementations and creates a persistent synchronization gap between client and server. The vulnerability affects multiple version ranges including 8.0.0 through 8.1.9, 9.0.0 through 9.2.14, and 10.0.0 through 10.1.3, indicating this was a longstanding issue that persisted across major releases.
From an operational impact perspective, this vulnerability creates a significant risk of header block corruption that can affect all subsequent HTTP/2 communications on affected connections. Attackers could potentially exploit this to cause service degradation, connection failures, or even information leakage through malformed header data interpretation. The flaw directly impacts the reliability and security of web traffic handling capabilities within Apache Traffic Server deployments, particularly in high-traffic environments where HTTP/2 is actively utilized. This vulnerability aligns with CWE-691 which addresses inadequate synchronization in protocol implementations and represents a specific instance of improper state management during protocol operations.
The mitigation strategy requires immediate deployment of patched versions 9.2.15 or 10.1.4, which implement proper encoding validation before dynamic table updates. Organizations should conduct thorough testing of the updated versions in their environments to ensure compatibility with existing configurations and traffic patterns. Security teams should monitor affected deployments for potential exploitation attempts and consider implementing additional network monitoring to detect unusual header block corruption patterns that might indicate this vulnerability being actively exploited.
This vulnerability demonstrates a critical failure in protocol implementation security where basic state management principles were not properly enforced during HTTP/2 processing. The issue highlights the importance of proper error handling and state synchronization in high-performance web server implementations, particularly when dealing with complex compression protocols like HPACK. The ATT&CK framework would categorize this under privilege escalation through protocol manipulation, as successful exploitation could potentially lead to more severe impacts including service disruption or data integrity compromise. Organizations relying on Apache Traffic Server should prioritize immediate patching to prevent potential exploitation and maintain the security posture of their web infrastructure.