CVE-2026-15311: NousResearch hermes-agent Matrix Adapter matrix.py MatrixAdapter._markdown_to_html cross site scripting

Severity: low (CVSS 3.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-10 · updated 2026-10-25
Weakness: CWE-79

Description

A vulnerability was identified in NousResearch hermes-agent up to 2026.5.29.2. Affected by this issue is the function MatrixAdapter._markdown_to_html of the file gateway/platforms/matrix.py of the component Matrix Adapter. Such manipulation leads to cross site scripting. The attack can be executed remotely. The exploit is publicly available and might be used. The pull request to fix this issue awaits acceptance.

Affected products

NousResearch hermes-agent: 2026.5.29.0, 2026.5.29.1, 2026.5.29.2

References

https://github.com/NousResearch/hermes-agent/
https://github.com/NousResearch/hermes-agent/issues/42667
https://github.com/NousResearch/hermes-agent/pull/42759
https://vuldb.com/cve/CVE-2026-15311
https://vuldb.com/submit/852843
https://vuldb.com/vuln/377247
https://vuldb.com/vuln/377247/cti

Get alerted when CVE-2026-15311 or the next vulnerability affects your stack