---
id: "CVE-2026-119559"
kind: "vulnerability"
aliases: ["CVE-2026-119559"]
title: "OpenLiteSpeed: HTTP/3 lets attackers skip client certificate checks on virtual hosts"
severity: "high"
cvss: 8.2
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["http3", "mtls", "openlitespeed", "runtime", "self-hosted"]
not_affected_if: ["http3-disabled", "no-mtls-vhosts"]
published_at: "2026-10-30T12:16:43+00:00"
first_seen_at: "2026-10-30T12:30:26+00:00"
updated_at: "2026-10-30T12:32:11+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-119559", "first_seen_at": "2026-10-30T12:30:26+00:00"}]
---

# OpenLiteSpeed: HTTP/3 lets attackers skip client certificate checks on virtual hosts

OpenLiteSpeed through 1.9.4 accepts HTTP/3 connections without enforcing a virtual host's client certificate requirement, because a certificate verification routine always returns true. An unauthenticated remote attacker can send a non-mTLS host's SNI with a protected Host header and reach content meant to require a client certificate.

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

## How to check

- Check the installed OpenLiteSpeed version against the `1.9.4` range stated in the advisory.
- Look for virtual hosts that require client certificates (mTLS) and confirm whether HTTP/3 (QUIC) is enabled on the listener serving them.

## Fix

- Fixed version: unknown; the sources do not name one.

## Timeline

- 2026-10-30T12:30:26+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-119559

## From the sources

OpenLiteSpeed through 1.9.4 contains an authentication bypass vulnerability that allows unauthenticated remote attackers to evade virtual host client certificate requirements over HTTP/3. Because QuicStream inherits a verifyContext() implementation that always returns true, attackers can present a non-mTLS host's SNI with a protected Host header to access protected content.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_