Vulnerability · Published Jun 17, 2026 · Assigned by VulnCheck

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

Medium 6.5

In plain English

A medium-severity authorization bypass via user-controlled key in hermes-webui from nesquena. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium

Exploit odds (30 days)0.3%top 71.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
nesquena	hermes-webui	0 – before 0.51.443

Weakness: CWE-639 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

References

hermes-webui v0.51.443 Release Notes release-notes
Researcher Pull Request issue-tracking, patch
Maintainer Pull Request issue-tracking, patch
Patch Commit patch
https://www.vulncheck.com/advisories/hermes-webui-broken-access-control-in-api-session-endpoint third-party-advisory