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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-32136: 0.77% estimated exploitation activity in the next 30 days; percentile 55.49 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

VULNERABILITY: HTTP/2 Cleartext (h2c) Upgrade Authentication Bypass ======================================================================== Severity: CRITICAL CVSS 3.1: 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) CWE: CWE-287 (Improper Authentication) Component: internal/home/web.go Affected: AdGuardHome (tested on v0.107.72) ------------------------------------------------------------------------ Summary ------------------------------------------------------------------------ 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. ------------------------------------------------------------------------…

Published by the source

12 Mar 2026, 14:47 UTC

Last modified by the source

12 Mar 2026, 14:47 UTC

Source last checked

26 Oct 2026, 15:18 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5fg6-wrq4-w5gh

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# Patch Next advisory brief: CVE-2026-32136

Advisory: AdGuard Home: HTTP/2 Cleartext (h2c) Upgrade Authentication Bypass
IDs: CVE-2026-32136, GHSA-5fg6-wrq4-w5gh
Record: https://patchnext.com/advisories/cve-2026-32136 (revision 1, source checked 26 Oct 2026, 15:18 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/AdguardTeam/AdGuardHome 0.107.73. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/AdguardTeam/AdGuardHome: affected < 0.107.73; fixed in 0.107.73

## Suggested inspection (read-only)
- Go github.com/AdguardTeam/AdGuardHome: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/AdguardTeam/AdGuardHome.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5fg6-wrq4-w5gh (GitHub-reviewed advisory GHSA-5fg6-wrq4-w5gh lists affected ranges: Go github.com/AdguardTeam/AdGuardHome >=0 <0.107.73)

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