CVE-2026-111810 in Traffic Server
Summary
by MITRE • 10/21/2026
Apache Traffic Server 9.2.15, 10.1.4 and 10.2.0 write one unthrottled diagnostic log line for every internal @ header they strip, so a request carrying many such headers makes the proxy write far more log data than the request contains.
This issue affects Apache Traffic Server: 9.2.15, 10.1.4, 10.2.0.
Users are recommended to upgrade to version 9.2.16, 10.1.5, or 10.2.1, which fix the issue.
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Analysis
by VulDB Data Team • 10/21/2026
The vulnerability identified in Apache Traffic Server versions 9.2.15, 10.1.4, and 10.2.0 represents a significant resource exhaustion risk stemming from uncontrolled log generation during header processing. This flaw is categorized under CWE-770: Allocation of Resources Without Limits or Throttling, as the application fails to restrict the volume of diagnostic output relative to the input size. The core technical issue arises when the proxy encounters HTTP requests containing multiple internal @ headers that require stripping. Instead of logging these events once per request or implementing a rate-limiting mechanism for such specific log entries, the server generates one unthrottled diagnostic line for each individual header stripped. This linear scaling of output against input complexity creates an asymmetric resource consumption pattern where a relatively small number of malicious requests can trigger disproportionately large amounts of disk I/O and CPU usage dedicated to logging operations rather than actual request handling or response generation.
From an operational perspective, this behavior exposes the infrastructure to Denial of Service (DoS) attacks with minimal effort from an adversary. An attacker can craft HTTP requests containing a high volume of internal @ headers designed specifically to trigger the stripping logic repeatedly within a single transaction. As Apache Traffic Server processes these requests in production environments where logging is typically enabled for audit and debugging purposes, the continuous generation of diagnostic lines rapidly fills available disk space or saturates I/O bandwidth. This resource contention can lead to service degradation for legitimate users, potential crashes due to out-of-memory conditions if logs are buffered in memory before flushing, or complete unavailability of the proxy layer. The impact is particularly severe because it targets a fundamental logging subsystem that often runs with high privileges and continuous availability requirements, making it an attractive vector for disrupting critical web infrastructure without requiring complex exploitation techniques beyond standard HTTP request manipulation.
The attack surface aligns closely with ATT&CK technique T1496: Resource Hijacking, specifically through the exhaustion of system resources via inefficient processing logic. By leveraging the verbose logging behavior inherent to diagnostic modes or default configurations in these affected versions, an attacker can effectively hijack server capacity for denial purposes. The vulnerability highlights a common oversight in software development where internal cleanup operations are coupled with excessive observability outputs without considering scalability under adversarial conditions. This lack of throttling means that even low-bandwidth connections from distributed botnets could collectively overwhelm the logging subsystems if not properly mitigated, as each node contributes to the cumulative log volume through simple header injection rather than requiring high-volume traffic patterns typically associated with volumetric DoS attacks.
To mitigate this vulnerability and restore secure operational stability, organizations running Apache Traffic Server must upgrade immediately to version 9.2.16, 10.1.5, or 10.2.1, where the logging logic has been corrected to prevent unbounded output generation during header stripping operations. Until an upgrade is feasible, administrators should consider implementing rate-limiting rules at a preceding reverse proxy or load balancer layer to restrict the number of requests containing excessive headers from reaching the vulnerable Apache Traffic Server instances. Additionally, temporarily reducing log verbosity for diagnostic messages related to internal header processing can serve as a short-term workaround to limit disk I/O impact, although this reduces visibility into potential security events and is not a sustainable solution. Regular patch management practices are essential to ensure that such resource exhaustion flaws do not persist in production environments where availability is paramount.