# CVE-2026-55197: Hermes WebUI broken access control in /api/session endpoint

Source: https://junglewise.ai/threats/cve-2026-55197-hermes-webui-broken-access-control-in-api-session-endpoint  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-17. Updated: 2026-06-20  
License: CC BY 4.0 with a link back

CVE-2026-55197 · Severity: medium · CVSS 6.5 · Published 2026-06-17

Hermes WebUI, a tool for managing AI agent sessions and profiles, contains a security flaw where users can view conversation transcripts belonging to other profiles. By manually entering a session ID, an authenticated user can bypass the normal interface restrictions that usually keep different profiles separate. This could lead to the unauthorized disclosure of sensitive chat history and metadata from other users or organizational units.

Technologies: [Nesquena Hermes WebUI](https://junglewise.ai/threats/technologies/hermes-webui). Vendors: [Nesquena](https://junglewise.ai/threats/vendors/nesquena).

## Quick answers

**Is CVE-2026-55197 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55197 being exploited in the wild.

**How severe is CVE-2026-55197?** Medium severity, with a CVSS score of 6.5, published 17 June 2026.

**Which products and versions are affected?** Nesquena Hermes WebUI < 0.51.443.

**Is there a fix for CVE-2026-55197?** A patch was published on 2026-06-15: Version 0.51.443 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55197 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-55197?** Check whether you run Nesquena Hermes WebUI at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A broken access control vulnerability (CWE-639) exists in the /api/session endpoint of Hermes WebUI. While the main session list endpoint correctly filters results based on the user's active profile, the detail endpoint failed to perform a profile-matching check when a specific session_id was provided. An authenticated attacker with knowledge of a session ID belonging to a different profile could retrieve full conversation transcripts and metadata via a GET request to /api/session?session_id=<foreign_id>&messages=1. The vulnerability was addressed in version 0.51.443 by implementing the _profiles_match check on the detail and export routes.

## Affected products

- nesquena hermes-webui < 0.51.443

## Timeline

- 2026-06-11: other: Fix proposed in pull request #3982
- 2026-06-15: patched: Version 0.51.443 released
- 2026-06-17: disclosed: CVE-2026-55197 published

## References

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

## Related threats

- [nesquena Hermes WebUI unauthenticated RCE in terminal API](https://junglewise.ai/threats/cve-2026-58123-nesquena-hermes-webui-unauthenticated-rce-in-terminal-api)
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- [nesquena Hermes WebUI authorization bypass in session export endpoint](https://junglewise.ai/threats/cve-2026-55198-nesquena-hermes-webui-authorization-bypass-in-session-export)
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