NousResearch hermes-agent Matrix Adapter matrix.py MatrixAdapter._markdown_to_html cross site scripting (CVE-2026-15311) | HOL Guard CVE

Low · CVSS 3.5CVE-2026-15311

NousResearch hermes-agent Matrix Adapter matrix.py MatrixAdapter._markdown_to_html cross site scripting

Answer in brief

CVE-2026-15311 records a Low severity (CVSS 3.5) vulnerability in NousResearch hermes-agent Matrix Adapter matrix.py MatrixAdapter._markdown_to_html cross site scripting. The current sources do not mark it as known exploited. The current feed maps NousResearch/hermes-agent (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 9, 2026Updated Jul 10, 2026Source checked Sep 19, 2026First seen by HOL Jul 10, 2026Material review Jul 10, 2026

Upstream Advisory

Key facts

Risk: Low · CVSS 3.5
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

CVSS is 3.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps NousResearch/hermes-agent (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
NousResearch/hermes-agentgeneric	2026.5.29.0 \|\| 2026.5.29.1 \|\| 2026.5.29.2	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for NousResearch/hermes-agent.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Jul 9, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Jul 10, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jul 10, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.