What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-17 · updated 2026-10-26
• Weakness: CWE-639

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

• nesquena hermes-webui: before 0.51.443 — fixed in 0.51.443

How to fix

Upgrade to a fixed version: nesquena hermes-webui 0.51.443. Check the vendor advisory for mitigations.

References

• https://github.com/nesquena/hermes-webui/commit/2a3baa71b81ca92da8ece8616a09f15894beec71
• https://github.com/nesquena/hermes-webui/pull/3982
• https://github.com/nesquena/hermes-webui/pull/4269
• https://github.com/nesquena/hermes-webui/releases/tag/v0.51.443
• https://www.vulncheck.com/advisories/hermes-webui-broken-access-control-in-api-session-endpoint
• https://github.com/nesquena/hermes-webui/pull/3982

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