PatchSiren cyber security CVE debrief
CVE-2026-15311 NousResearch CVE debrief
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. Users of NousResearch hermes-agent up to 2026.5.29.2 should assess the risk of cross site scripting and apply patches or mitigations as available.
- Vendor
- NousResearch
- Product
- hermes-agent
- CVSS
- LOW 2
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-07-10
- Original CVE updated
- 2026-07-10
- Advisory published
- 2026-07-10
- Advisory updated
- 2026-07-10
Who should care
Users of NousResearch hermes-agent up to 2026.5.29.2 should assess the risk of cross site scripting and apply patches or mitigations as available. The vulnerability exists in the MatrixAdapter._markdown_to_html function of the gateway/platforms/matrix.py file in the Matrix Adapter component of NousResearch hermes-agent up to 2026.5.29.2.
Technical summary
The vulnerability exists in the MatrixAdapter._markdown_to_html function of the gateway/platforms/matrix.py file in the Matrix Adapter component of NousResearch hermes-agent up to 2026.5.29.2. This function is vulnerable to cross site scripting attacks when processing markdown input. The vulnerability has a CVSS score of 2 and a CVSS severity of LOW. Users of NousResearch hermes-agent up to 2026.5.29.2 should assess the risk of cross site scripting and apply patches or mitigations as available.
Defensive priority
Apply patches or mitigations for cross site scripting in NousResearch hermes-agent up to 2026.5.29.2. Implement input validation and output encoding for markdown processing. Monitor for and restrict exploitation attempts against the Matrix Adapter component.
Recommended defensive actions
- Apply available patches for NousResearch hermes-agent up to 2026.5.29.2
- Implement input validation and output encoding for markdown processing
- Monitor for and restrict exploitation attempts against the Matrix Adapter component
- Review compensating controls for exposed systems while remediation is scheduled and verified
- Check relevant monitoring, detection, and logs for exposed assets that need extra review
- Track exceptions, retest remediated assets, and close the item only after evidence is documented
- Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
Evidence notes
The CVE record was published on 2026-07-10T00:16:32.853Z and was last modified on 2026-07-10T15:43:30.330Z. The NVD entry is currently Deferred. The vulnerability exists in the MatrixAdapter._markdown_to_html function of the gateway/platforms/matrix.py file in the Matrix Adapter component of NousResearch hermes-agent up to 2026.5.29.2. This function is vulnerable to cross site scripting attacks when processing markdown input. Users of NousResearch hermes-agent up to 2026.5.29.2 should assess the risk of cross site scripting and apply patches or mitigations as available. The attack can be executed remotely.
Official resources
AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-10T00:16:32.853Z and has not been modified since then. The NVD entry is currently Deferred.