CVE-2026-55198

Description

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.

CVSS v3.1 Score

6.5

MEDIUM

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

EPSS — Exploit Prediction

0.0027

Probability of exploitation

0.19%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-639 CWE-639

References

Other References

https://github.com/nesquena/hermes-webui/commit/2a3baa71b81ca92da8ece8616a09f15894beec71 https://github.com/nesquena/hermes-webui/pull/3991 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-cross-profile-session-data-exfiltration-via-session-export-endpoint https://github.com/nesquena/hermes-webui/pull/3991

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-55198? +

CVE-2026-55198 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0027, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-55198? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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