VDB-377247 · Submit #852843 · CVE-2026-15311

NousResearch hermes-agent up to 2026.5.29.2 Matrix Adapter matrix.py MatrixAdapter._markdown_to_html cross site scripting

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
3.3	$0-$5k	0.56

Summaryinfo

A vulnerability has been found in NousResearch hermes-agent up to 2026.5.29.2 and classified as problematic. This affects the function MatrixAdapter._markdown_to_html of the file gateway/platforms/matrix.py of the component Matrix Adapter. Performing a manipulation results in cross site scripting. This vulnerability is reported as CVE-2026-15311. The attack is possible to be carried out remotely. Moreover, an exploit is present. The pull request to fix this issue awaits acceptance.

Detailsinfo

A vulnerability, which was classified as problematic, was found in NousResearch hermes-agent up to 2026.5.29.2. This affects the function MatrixAdapter._markdown_to_html of the file gateway/platforms/matrix.py of the component Matrix Adapter. The manipulation with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-15311. The exploitability is told to be easy. It is possible to initiate the attack remotely. It demands that the victim is doing some kind of user interaction. Technical details and a public exploit are known. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

The exploit is shared for download at github.com. It is declared as proof-of-concept. The pull request to fix this issue awaits acceptance.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-42764). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

NousResearch

Name

hermes-agent

Version

Website

Product: https://github.com/NousResearch/hermes-agent/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 3.5
VulDB Meta Temp Score: 3.3

VulDB Base Score: 3.5
VulDB Temp Score: 3.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
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Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Cross site scripting
CWE: CWE-79 / CWE-94 / CWE-74
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Access: Public
Status: Proof-of-Concept
Download: 🔒
Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

07/09/2026 Advisory disclosed
07/09/2026 +0 days VulDB entry created
07/10/2026 +1 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: 42667
Status: Confirmed
Confirmation: 🔒

CVE: CVE-2026-15311 (🔒)
GCVE (CVE): GCVE-0-2026-15311
GCVE (VulDB): GCVE-100-377247
EUVD: 🔒
scip Labs: https://www.scip.ch/en/?labs.20161013

Entryinfo

Created: 07/09/2026 19:54
Updated: 07/10/2026 05:04
Changes: 07/09/2026 19:54 (59), 07/10/2026 05:04 (1)
Complete: 🔍
Submitter: Eric-d
Cache ID: 216::103

Submitinfo

Accepted

Submit #852843: NousResearch hermes-agent 2026.5.29.2 Cross-site Scripting (CWE-79) (by Eric-d)