CVE-2026-58155 in Traffic Server
Summary
by MITRE • 07/29/2026
Apache Traffic Server truncates over-long header names, allowing header aliasing, request smuggling, and policy bypass.
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 in Apache Traffic Server represents a critical security flaw that stems from improper handling of HTTP header names during processing. The core issue occurs when the system encounters header names exceeding its internal buffer limits, leading to automatic truncation of these names. This truncation behavior creates opportunities for attackers to exploit header aliasing mechanisms where multiple headers with different names but similar truncated representations can be treated as equivalent by the server.
The technical implementation flaw resides in how the HTTP parser within Traffic Server manages header name validation and storage. When header names exceed configured maximum lengths, the system performs silent truncation rather than rejecting malformed requests outright. This design decision enables attackers to craft HTTP requests where carefully constructed header names, when truncated, map to existing legitimate headers or create ambiguous representations that bypass normal security controls.
The operational impact of this vulnerability spans multiple security domains including HTTP request smuggling attacks, policy enforcement bypasses, and potential service disruption scenarios. Attackers can leverage header aliasing to manipulate how the server processes requests, potentially allowing them to bypass access control mechanisms, circumvent rate limiting policies, or inject malicious content through crafted header combinations. The vulnerability's scope extends across multiple major versions of Traffic Server, making it particularly concerning for organizations maintaining legacy deployments.
This issue aligns with CWE-129 and CWE-770 in the Common Weakness Enumeration catalog, specifically addressing weaknesses related to improper input validation and buffer overflows in HTTP processing components. The vulnerability also maps to ATT&CK technique T1566 which covers phishing attacks through malicious headers, and T1071.004 for application layer protocol manipulation. Organizations using Traffic Server across versions 8.0.0 through 8.1.9, 9.0.0 through 9.2.14, and 10.0.0 through 10.1.3 face significant risk from this flaw, as the truncation behavior creates predictable attack vectors.
The recommended mitigation involves upgrading to version 9.2.15 or 10.1.4 which implement proper header validation mechanisms that either reject overly long header names or handle them consistently without creating aliasing opportunities. Organizations should also consider implementing additional monitoring for unusual header patterns and conduct thorough testing of their Traffic Server configurations before applying the patches. Network administrators should review existing security policies to ensure they account for proper header length validation and implement logging mechanisms that can detect potential exploitation attempts through malformed header combinations.
Additional defensive measures include configuring explicit header name length limits at the proxy level, implementing comprehensive request filtering rules, and establishing monitoring procedures that alert on unusual header patterns or repeated truncation events. The fix addresses the root cause by ensuring that header processing maintains consistent behavior regardless of input length, eliminating the possibility of attackers manipulating the system through carefully crafted header names that exploit the original truncation mechanism.