CVE-2026-9354
NousResearch hermes-agent Slack Agent/Mattermost Agent escape output
Description
A vulnerability was detected in NousResearch hermes-agent up to 2026.4.16. The affected element is an unknown function of the component Slack Agent/Mattermost Agent. The manipulation of the argument format_message results in escaping of output. The attack can be executed remotely. The exploit is now public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.
INFO
Published Date :
May 24, 2026, 5:16 a.m.
Last Modified :
July 23, 2026, 11:10 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 2.0 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Validate and sanitize all external inputs.
- Update the agent software to the latest version.
- Apply vendor-provided security patches immediately.
- Review agent code for similar vulnerabilities.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-9354.
| URL | Resource |
|---|---|
| https://gist.github.com/YLChen-007/e90fb38ac03284176bae49898a3a46a4 | |
| https://vuldb.com/submit/812226 | |
| https://vuldb.com/vuln/365317 | |
| https://vuldb.com/vuln/365317/cti |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-9354 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-9354
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-9354 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-9354 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Jul. 23, 2026
Action Type Old Value New Value Added Translation Title: hermes-agent de NousResearch, Description: Una vulnerabilidad fue detectada en NousResearch hermes-agent hasta 2026.4.16. El elemento afectado es una función desconocida del componente Slack Agent/Mattermost Agent. La manipulación del argumento format_message resulta en el escape de la salida. El ataque puede ser ejecutado remotamente. El exploit es ahora público y puede ser utilizado. El proveedor fue contactado tempranamente sobre esta divulgación pero no respondió de ninguna manera. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:2.3:a:nousresearch:hermes-agent:*:*:*:*:*:*:*:*'], 'vendor': 'NousResearch', 'modules': ['Slack Agent/Mattermost Agent'], 'product': 'hermes-agent', 'versions': [{'status': 'affected', 'version': '2026.4.0'}, {'status': 'affected', 'version': '2026.4.1'}, {'status': 'affected', 'version': '2026.4.2'}, {'status': 'affected', 'version': '2026.4.3'}, {'status': 'affected', 'version': '2026.4.4'}, {'status': 'affected', 'version': '2026.4.5'}, {'status': 'affected', 'version': '2026.4.6'}, {'status': 'affected', 'version': '2026.4.7'}, {'status': 'affected', 'version': '2026.4.8'}, {'status': 'affected', 'version': '2026.4.9'}, {'status': 'affected', 'version': '2026.4.10'}, {'status': 'affected', 'version': '2026.4.11'}, {'status': 'affected', 'version': '2026.4.12'}, {'status': 'affected', 'version': '2026.4.13'}, {'status': 'affected', 'version': '2026.4.14'}, {'status': 'affected', 'version': '2026.4.15'}, {'status': 'affected', 'version': '2026.4.16'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-9354', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-05-27T16:25:19.177335Z'} -
New CVE Received by [email protected]
May. 24, 2026
Action Type Old Value New Value Added Description A vulnerability was detected in NousResearch hermes-agent up to 2026.4.16. The affected element is an unknown function of the component Slack Agent/Mattermost Agent. The manipulation of the argument format_message results in escaping of output. The attack can be executed remotely. The exploit is now public and may be used. The vendor was contacted early about this disclosure but did not respond in any way. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L Added CVSS V2 (AV:N/AC:L/Au:N/C:N/I:P/A:P) Added CWE CWE-74 Added CWE CWE-116 Added Reference https://gist.github.com/YLChen-007/e90fb38ac03284176bae49898a3a46a4 Added Reference https://vuldb.com/submit/812226 Added Reference https://vuldb.com/vuln/365317 Added Reference https://vuldb.com/vuln/365317/cti