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

Synopsis

Broken access control in the Hermes WebUI /api/session endpoint allows an authenticated user to read conversation transcripts and metadata belonging to other profiles. The vulnerability is reachable over the network and requires only a low-privilege account; no victim interaction is needed. Successful exploitation gives the attacker unauthorized read access to session transcripts and metadata across profile boundaries. A patched-image rebuild at version 0.51.443 is available on HarborGuard for environments running an affected version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The /api/session endpoint is exposed over the network, so an attacker must be able to reach the service via HTTP/HTTPS.

• AuthenticationRequired

  Any low-privilege account is sufficient; the attacker does not need admin rights, but a valid session credential is required.

• Victim interactionNot required

  The attacker queries the endpoint directly with no need to involve or deceive another user.

• Attack complexityDetail

  Exploitation is reliable and condition-free; the attacker only needs to substitute a foreign session ID in a standard GET request.

Blast Radius

• The attacker reads full conversation transcripts from sessions belonging to other profiles, exposing any sensitive content exchanged in those sessions.
• Session metadata such as session IDs, timing, and profile associations is also disclosed, enabling further enumeration of other users' activity.
• Confidentiality of all sessions accessible via the /api/session endpoint is compromised; no data is modified and no service availability impact occurs.