CVE-2026-33930 in Traffic Server
Summary
by MITRE • 07/29/2026
Apache Traffic Server copies the client Host header into a fixed-size stack buffer without a bound during redirect handling, so an over-long Host header overflows the stack when redirect following is enabled.
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 • 07/30/2026
The vulnerability in Apache Traffic Server represents a classic stack buffer overflow condition that emerges during HTTP redirect processing when the client Host header exceeds predetermined size limits. This flaw exists within the server's handling of redirect responses where it copies the client-provided Host header into a fixed-size stack buffer without proper bounds checking mechanisms. The issue manifests specifically when redirect following is enabled, creating a scenario where an attacker can craft a maliciously long Host header to trigger memory corruption.
The technical implementation of this vulnerability stems from improper input validation within the HTTP request processing pipeline of Apache Traffic Server. When a client sends an HTTP request containing a Host header that exceeds the allocated stack buffer size, the copying operation overflows into adjacent memory segments, potentially corrupting other stack variables or even executable code. This type of vulnerability falls under the CWE-121 category of Stack-based Buffer Overflow, where insufficient bounds checking allows data to overwrite adjacent stack memory regions. The affected versions span multiple major releases including 8.0.0 through 8.1.9, 9.0.0 through 9.2.14, and 10.0.0 through 10.1.3, indicating a prolonged exposure window that could have allowed for exploitation across various deployment environments.
The operational impact of this vulnerability extends beyond simple memory corruption, as it creates potential attack vectors for remote code execution or denial of service conditions. An attacker exploiting this flaw could manipulate the stack contents to redirect program execution flow, potentially leading to arbitrary code execution on the target server. The vulnerability's relevance within the ATT&CK framework aligns with techniques involving buffer overflow exploitation and privilege escalation through memory corruption. Systems utilizing Apache Traffic Server in redirect-enabled configurations face heightened risk, particularly when processing untrusted client input. The attack surface is amplified in environments where the server acts as a reverse proxy or load balancer, as these roles typically involve more extensive HTTP header processing and redirect handling.
Mitigation strategies focus primarily on upgrading to patched versions 9.2.15 or 10.1.4, which implement proper bounds checking for Host header values during redirect processing. Organizations should also consider implementing additional defensive measures including input validation at network boundaries, rate limiting for suspicious header sizes, and monitoring for anomalous HTTP request patterns. The fix addresses the root cause by introducing proper buffer size validation before copying client headers into internal buffers, preventing the overflow condition that enables exploitation. Security teams should conduct comprehensive testing of upgraded systems to ensure that the patch does not introduce regressions in legitimate redirect functionality while maintaining the enhanced security posture against this specific memory corruption vulnerability.