---
id: "CVE-2026-111815"
kind: "vulnerability"
aliases: ["CVE-2026-111815"]
title: "Apache Traffic Server: TLS session resumption skips client certificate check across SNI hosts"
severity: "critical"
cvss: 10.0
epss: 0.00172
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["apache-traffic-server", "mtls", "runtime", "self-hosted", "tls"]
not_affected_if: ["default-config", "no-verify-client-strict"]
published_at: "2026-10-21T20:17:23+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-2026-111815", "first_seen_at": "2026-10-23T21:57:29+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-111815", "first_seen_at": "2026-10-24T13:15:54+00:00"}]
---

# Apache Traffic Server: TLS session resumption skips client certificate check across SNI hosts

Apache Traffic Server can resume a TLS session on a virtual host that requires client certificates without checking the certificate again. An attacker who holds a session from a permissive host may reach a strict mTLS host without presenting a valid client certificate.

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

## How to check

Check the installed version with traffic_server --version and compare it to the affected ranges 8.0.0-8.1.11, 9.0.0-9.2.15, 10.0.0-10.1.4 and 10.2.0.
If you use verify_client STRICT in sni.yaml, you are in scope.

## Fix

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

## Timeline

- 2026-10-23T21:57:29+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-111815
- 2026-10-24T13:15:54+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-111815

## From the sources

Apache Traffic Server can resume a TLS session across SNI virtual hosts without re-verifying a client certificate required by the resumed host's verify_client STRICT policy.



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_