---
id: "CVE-2026-111809"
kind: "vulnerability"
aliases: ["CVE-2026-111809"]
title: "Apache Traffic Server: HEAD requests enable request smuggling past proxies"
severity: "critical"
cvss: 9.3
epss: 0.00218
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["apache-traffic-server", "infrastructure", "runtime", "self-hosted"]
not_affected_if: ["managed-hosting"]
published_at: "2026-10-21T20:17:22+00:00"
first_seen_at: "2026-10-23T21:57:29+00:00"
updated_at: "2026-10-24T13:15:54+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-111809", "first_seen_at": "2026-10-23T21:57:29+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-111809", "first_seen_at": "2026-10-24T13:15:54+00:00"}]
---

# Apache Traffic Server: HEAD requests enable request smuggling past proxies

Apache Traffic Server mishandles HEAD requests that carry Content-Length or Transfer-Encoding headers, letting a remote attacker desynchronize request parsing. An attacker can smuggle requests through the proxy to reach back-end handling that should be blocked.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

Check the running version, for example with traffic_server -V or the installed package version; affected are 8.0.0 to 8.1.11, 9.0.0 to 9.2.15, 10.0.0 to 10.1.4, and 10.2.0.

## Fix

Upgrade to 9.2.16, 10.1.5, or 10.2.1, matching your major line.

## Timeline

- 2026-10-23T21:57:29+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-111809
- 2026-10-24T13:15:54+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-111809

## From the sources

Apache Traffic Server allows request smuggling via HEAD requests that carry Content-Length or Transfer-Encoding.



This issue affects Apache Traffic Server: from 8.0.0 through 8.1.11, from 9.0.0 through 9.2.15, from 10.0.0 through 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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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_