Auth bypass in Nesquena Hermes-Webui
CVE-2026-55198
Hermes WebUI before 0.51.443 contains an authorization bypass vulnerability in the session export endpoint that allows authenticated users to access sessions from other profiles. The _handle_session_export handler in api/routes.py fails to verify active-profile ownership before serializing session data, enabling attackers to exfiltrate foreign session transcripts by guessing or knowing session identifiers.
Vulnerability class: IDOR (Insecure Direct Object Reference)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.005 (38.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 38.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- Nesquena Hermes-Webui — versions 0, 0.51.443
Weakness classification (CWE)
References
- github.com/nesquena/hermes-webui/releases/tag/v0.51.443 (release-notes)
- github.com/nesquena/hermes-webui/pull/3991 (issue-tracking, technical-description, patch)
- github.com/nesquena/hermes-webui/pull/4269 (issue-tracking, patch)
- github.com/nesquena/hermes-webui/commit/2a3baa71b81ca92da8ece8616a09f15894beec71 (patch)
- www.vulncheck.com/advisories/hermes-webui-cross-profile-session-data-exfiltrati… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-55198?
- CVE-2026-55198 is a medium-severity vulnerability in Nesquena Hermes-Webui, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 6.5/10. Published 2026-06-17.
- How severe is CVE-2026-55198?
- Medium severity. CVSS v3 base score is 6.5 out of 10.