CVE-2026-55198: Hermes WebUI < 0.51.443 - Cross-Profile Session Data Exfiltration via Session Export Endpoint

Synopsis

An authorization bypass in the session export endpoint of Hermes WebUI (versions before 0.51.443) lets any authenticated user read session data belonging to other user profiles. The vulnerability is reachable over the network and requires only a low-privilege account, with no additional interaction from a victim. Successful exploitation gives an attacker full read access to foreign session transcripts, including conversation history and any sensitive data captured in those sessions. 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 session export endpoint is exposed over the network, so an attacker must be able to reach the service via HTTP/HTTPS.

• AuthenticationRequired

  Any low-privilege authenticated account is sufficient; no administrative or elevated permissions are needed.

• Victim interactionNot required

  No action from another user is needed; the attacker directly calls the export endpoint without any social-engineering step.

• Attack complexityDetail

  Exploitation is reliable and condition-free once the attacker has a valid session ID to target; no race conditions or special environmental factors apply.

Blast Radius

• The attacker reads full session transcripts from other users' profiles, including all conversation history stored in those sessions.
• Any sensitive or confidential information a user typed into Hermes WebUI during a session is exposed to the attacker.
• Session identifiers for foreign sessions can be harvested, enabling the attacker to chain further unauthorized actions against those sessions.
• Integrity and availability of the targeted data are not directly affected; the impact is confined to confidentiality of session data.