Cross-Site Scripting Vulnerability in NousResearch Hermes-Agent's Matrix Adapter
CVE-2026-15311

5.1MEDIUM

Key Information:

Vendor

Nousresearch

Status
Hermes-agent
Vendor
CVE Published:
9 July 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-15311?

A cross-site scripting vulnerability exists in the Matrix Adapter component of NousResearch's Hermes-Agent, specifically in the MatrixAdapter._markdown_to_html function located in the gateway/platforms/matrix.py file. This flaw allows attackers to execute scripts remotely by manipulating markdown inputs, potentially leading to unauthorized actions on behalf of users. The exploit is publicly known, and a pull request to address this issue is currently pending acceptance.

Affected Version(s)

hermes-agent 2026.5.29.0

hermes-agent 2026.5.29.1

hermes-agent 2026.5.29.2

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-15311 - Proof of Concept

References

https://vuldb.com/vuln/377247
vdb-entrytechnical-description
https://vuldb.com/vuln/377247/cti
signaturepermissions-required
https://vuldb.com/cve/CVE-2026-15311
third-party-advisory

CVSS V4

Score:
5.1
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Eric-d (VulDB User)
VulDB CNA Team
.