CVE-2026-32136CWE-287

AdGuard Home: HTTP/2 Cleartext (h2c) Upgrade Authentication Bypass

Critical · published March 11, 2026

CVSS v3.1
9.8
EPSS
1%
Percentile
56.6
In the wild
Unconfirmed
What it is

AdGuard Home is a network-wide software for blocking ads and tracking. Prior to 0.107.73, an unauthenticated remote attacker can bypass all authentication in AdGuardHome by sending an HTTP/1.1 request that requests an upgrade to HTTP/2 cleartext (h2c). Once the upgrade is accepted, the resulting HTTP/2 connection is handled by the inner mux, which has no authentication middleware attached. All subsequent HTTP/2 requests on that connection are processed as fully authenticated, regardless of whether any credentials were provided. This vulnerability is fixed in 0.107.73.

The record
Technical detail
CVSS v3.1
9.8 · CRITICAL
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.00813 · 56.6th percentile
Weakness
CWE-287 · Improper Authentication
Published
2026-03-11T21:42Z
EPSS history
Timeline
  • 11 MAR 21:42Z
    AdGuard Home: HTTP/2 Cleartext (h2c) Upgrade Authentication Bypass
    cvelistv5