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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.

PUBLISHED Reserved 2026-05-23 | Published 2026-05-24 | Updated 2026-05-27 | Assigner VulDB




MEDIUM: 6.9CVSS: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
MEDIUM: 6.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L/E:P/RL:X/RC:R
MEDIUM: 6.5CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L/E:P/RL:X/RC:R
6.4AV:N/AC:L/Au:N/C:N/I:P/A:P/E:POC/RL:ND/RC:UR

Problem types

Escaping of Output

Injection

Product status

2026.4.0
affected

2026.4.1
affected

2026.4.2
affected

2026.4.3
affected

2026.4.4
affected

2026.4.5
affected

2026.4.6
affected

2026.4.7
affected

2026.4.8
affected

2026.4.9
affected

2026.4.10
affected

2026.4.11
affected

2026.4.12
affected

2026.4.13
affected

2026.4.14
affected

2026.4.15
affected

2026.4.16
affected

Timeline

2026-05-23:Advisory disclosed
2026-05-23:VulDB entry created
2026-05-23:VulDB entry last update

Credits

Eric-i (VulDB User) reporter

VulDB CNA Team coordinator

References

vuldb.com/vuln/365317 (VDB-365317 | NousResearch hermes-agent Slack Agent/Mattermost Agent escape output) vdb-entry technical-description

vuldb.com/vuln/365317/cti (VDB-365317 | CTI Indicators (IOB, IOC, IOA)) signature permissions-required

vuldb.com/submit/812226 (Submit #812226 | NousResearch hermes-agent 2026.4.16 Improper Encoding or Escaping of Output (CWE-116)) third-party-advisory

gist.github.com/YLChen-007/e90fb38ac03284176bae49898a3a46a4 exploit

cve.org (CVE-2026-9354)

nvd.nist.gov (CVE-2026-9354)

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