Vulnerability in Nousresearch Hermes-Agent
CVE-2026-9354
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 · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L.
EPSS exploit prediction
EPSS: 0.006 (46.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 46th percentile — 46.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.006 · change: +0.002
Affected products
- Nousresearch Hermes-Agent — versions 2026.4.0, 2026.4.1, 2026.4.2
Weakness classification (CWE)
References
- vuldb.com/vuln/365317 (technical-description, vdb-entry)
- vuldb.com/vuln/365317/cti (signature, permissions-required)
- vuldb.com/submit/812226 (third-party-advisory)
- gist.github.com/YLChen-007/e90fb38ac03284176bae49898a3a46a4 (exploit)
Frequently asked questions
- What is CVE-2026-9354?
- CVE-2026-9354 is a medium-severity vulnerability in Nousresearch Hermes-Agent, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 6.5/10. Published 2026-05-24.
- How severe is CVE-2026-9354?
- Medium severity. CVSS v3 base score is 6.5 out of 10.