CVE-2026-9354

NousResearch hermes-agent Slack Agent/Mattermost Agent escape output

State: Published
Severity: 6.9 Medium
Published: May 24, 2026
Updated: May 27, 2026
Reserved: May 23, 2026

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.

Scores

CVSS	Score	Vector	Source
4.0	6.9 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:P	VulDB
3.1	6.5 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L/E:P/RL:X/RC:R	VulDB
3.0	6.5 Medium	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L/E:P/RL:X/RC:R	VulDB
2.0	6.4 Medium	AV:N/AC:L/Au:N/C:N/I:P/A:P/E:POC/RL:ND/RC:UR	VulDB

Weaknesses

CWE-116 Escaping of Output
CWE-74 Injection

Affected Products

Product	Versions
hermes-agentNousResearch	2026.4.0Affected 2026.4.1Affected 2026.4.2Affected 2026.4.3Affected 2026.4.4Affected 2026.4.5Affected 2026.4.6Affected 2026.4.7Affected 2026.4.8Affected 2026.4.9Affected 2026.4.10Affected 2026.4.11Affected 2026.4.12Affected 2026.4.13Affected 2026.4.14Affected 2026.4.15Affected 2026.4.16Affected

References

VDB-365317 | NousResearch hermes-agent Slack Agent/Mattermost Agent escape outputvdb-entrytechnical-description
VDB-365317 | CTI Indicators (IOB, IOC, IOA)signaturepermissions-required
Submit #812226 | NousResearch hermes-agent 2026.4.16 Improper Encoding or Escaping of Output (CWE-116)third-party-advisory
https://gist.github.com/YLChen-007/e90fb38ac03284176bae49898a3a46a4exploit

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