How severe is CVE-2026-9354?

CVE-2026-9354 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability low.

Is CVE-2026-9354 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-9354?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-9354 have an EU (EUVD) identifier?

Yes. CVE-2026-9354 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-31566.

When was CVE-2026-9354 published?

CVE-2026-9354 was published on 2026-05-24 and last updated on 2026-06-17.

CVE-2026-9354

CVE-2026-9354 is a medium-severity vulnerability with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-74.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 6.4
CVSS v4: 5.5
EPSS exploit prediction: 0% (26th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-31566
Weakness: CWE-74
Published: 2026-05-24
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-9354?: CVE-2026-9354 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability low.
Is CVE-2026-9354 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-9354?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-9354 have an EU (EUVD) identifier?: Yes. CVE-2026-9354 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-31566.
When was CVE-2026-9354 published?: CVE-2026-9354 was published on 2026-05-24 and last updated on 2026-06-17.

References

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