Which versions of Hermes WebUI are affected by CVE-2026-55197?

Hermes WebUI versions prior to 0.51.443 allow authenticated users to access conversation transcripts and metadata from other user profiles through an insecure direct object reference vulnerability.. A patch is available.

How to fix or mitigate CVE-2026-55197?

Within 24 hours: Identify all Hermes WebUI instances and confirm versions prior to 0.51.443 are in use; assess scope of multi-profile deployments and data sensitivity. Within 7 days: Deploy Hermes WebUI 0.51.443 or later to all affected systems. Within 30 days: Review audit logs for unauthorized cross-profile session access and document any detected unauthorized data exposure incidents.

Hermes WebUI CVE-2026-55197

Q: What is the CVSS score of CVE-2026-55197?

CVE-2026-55197 has a CVSS 4.0 base score of 7.1 (High). CVSS 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.3%.

HIGH

Authorization Bypass Through User-Controlled Key (CWE-639)

2026-06-17 VulnCheck

Authentication Bypass Hermes Webui

7.1

CVSS 4.0 · Vendor: VulnCheck

Severity by source

Vendor (VulnCheck) PRIMARY

7.1 HIGH

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

vuln.today AI

6.5 MEDIUM

Network-reachable API exploitable by any authenticated low-privilege user with no interaction; impact is confined to confidentiality of other profiles' transcripts, with no integrity or availability effect.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Lifecycle Timeline

Source Code Evidence Fetched

Jun 17, 2026 - 18:48 vuln.today

Analysis Generated

Jun 17, 2026 - 18:48 vuln.today

DescriptionCVE.org

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.

AnalysisAI

Cross-profile session disclosure in Hermes WebUI before 0.51.443 lets any authenticated user retrieve conversation transcripts and metadata belonging to other profiles by passing a foreign session_id to the /api/session endpoint. The flaw is a classic IDOR (CWE-639) where profile boundary checks are missing on by-id reads. No public exploit identified at time of analysis, but the trigger is a single trivial GET request and the upstream patch openly describes the fix as 'scope session by-id reads + exports to active profile,' which discloses the bypass.

Technical ContextAI

Hermes WebUI is a web frontend (maintained by nesquena on GitHub, CPE cpe:2.3:a:nesquena:hermes-webui) that organizes chat-style sessions under per-user 'profiles' for isolation. The /api/session endpoint serves session transcripts when called with session_id and messages=1, but pre-fix versions used the supplied session_id as a direct object reference without verifying that the session belonged to the caller's active profile - the textbook CWE-639 (Authorization Bypass Through User-Controlled Key) pattern. The fix in commit 2a3baa71 and PRs #3982/#4269 adds active-profile scoping to both by-id reads and export paths, indicating the authorization check was missing in more than one code path.

RemediationAI

Vendor-released patch: upgrade to Hermes WebUI 0.51.443 or later, which scopes session by-id reads and exports to the caller's active profile (commit 2a3baa71b81ca92da8ece8616a09f15894beec71, see https://github.com/nesquena/hermes-webui/releases/tag/v0.51.443). If immediate upgrade is not possible, restrict /api/session?session_id=...&messages=1 at a reverse proxy or WAF so that only requests where session_id matches a value bound to the authenticated user's profile are forwarded - this requires the proxy to know the user-to-profile mapping and will break legitimate by-id reads if misconfigured. As a coarser compensating control, limit Hermes WebUI accounts to a single profile per user or restrict network access to the UI to a trusted user population, accepting that this does not address malicious authenticated insiders. Rotate or audit any session transcripts whose confidentiality is sensitive, since past disclosures cannot be recalled.