CVE-2026-15311
LowCVSS 3.5Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
A Cross-Site Scripting (XSS) vulnerability was found in the Matrix Adapter component of NousResearch hermes-agent up to version 2026.5.29.2, specifically in the MatrixAdapter._markdown_to_html function of gateway/platforms/matrix.py. The attack can be executed remotely and the exploit is publicly available.
Risk Assessment
The risk involves remote execution of scripts in the victim's browser, potentially leading to session theft, account takeover, or leakage of sensitive organizational data.
Recommendation
Immediately update hermes-agent to a patched version once available, or apply temporary mitigations such as input sanitization in the _markdown_to_html function.
Original NVD description (English source)
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.