VDB-365317 · Submit #812226 · CVE-2026-9354

NousResearch hermes-agent up to 2026.4.16 Slack Agent/Mattermost Agent format_message escape output

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.
5.9	$0-$5k	0.00

Summaryinfo

A vulnerability, which was classified as critical, has been found in NousResearch hermes-agent up to 2026.4.16. The impacted element is an unknown function of the component Slack Agent/Mattermost Agent. This manipulation of the argument format_message causes escape output. This vulnerability is tracked as CVE-2026-9354. The attack is possible to be carried out remotely. Moreover, an exploit is present. The vendor was contacted early about this disclosure but did not respond in any way.

Detailsinfo

A vulnerability was found in NousResearch hermes-agent up to 2026.4.16. It has been declared as critical. Affected by this vulnerability is an unknown functionality of the component Slack Agent/Mattermost Agent. The manipulation of the argument format_message with an unknown input leads to a escape output vulnerability. The CWE definition for the vulnerability is CWE-116. The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved. As an impact it is known to affect integrity, and availability.

The advisory is shared at gist.github.com. This vulnerability is known as CVE-2026-9354. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details and also a public exploit are known.

It is possible to download the exploit at gist.github.com. It is declared as proof-of-concept. The vendor was contacted early about this disclosure but did not respond in any way.

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 databases at CNNVD (CNNVD-202605-4920) and EUVD (EUVD-2026-31566). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Vendor

NousResearch

Name

hermes-agent

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.5
VulDB Meta Temp Score: 5.9

VulDB Base Score: 6.5
VulDB Temp Score: 5.9
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: Escape output
CWE: CWE-116 / CWE-74 / CWE-707
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Access: Public
Status: Proof-of-Concept
Download: 🔒

EPSS Score: 🔒
EPSS Percentile: 🔒

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

05/23/2026 Advisory disclosed
05/23/2026 +0 days VulDB entry created
05/25/2026 +2 days VulDB entry last update

Sourcesinfo

Advisory: gist.github.com
Status: Not defined

CVE: CVE-2026-9354 (🔒)
GCVE (CVE): GCVE-0-2026-9354
GCVE (VulDB): GCVE-100-365317
EUVD: 🔒
CNNVD: CNNVD-202605-4920 - Hermes Agent 安全漏洞

scip Labs: https://www.scip.ch/en/?labs.20161013

Entryinfo

Created: 05/23/2026 11:24
Updated: 05/25/2026 16:33
Changes: 05/23/2026 11:24 (55), 05/25/2026 09:48 (1), 05/25/2026 16:33 (6)
Complete: 🔍
Submitter: Eric-i
Cache ID: 216::103

Submitinfo

Accepted

Submit #812226: NousResearch hermes-agent 2026.4.16 Improper Encoding or Escaping of Output (CWE-116) (by Eric-i)

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