How severe is CVE-2026-3116?

CVE-2026-3116 has a CVSS 3.x base score of 4.9, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-3116 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.

What products are affected by CVE-2026-3116?

CVE-2026-3116 affects Mattermost Mattermost Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-3116?

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

Does CVE-2026-3116 have an EU (EUVD) identifier?

Yes. CVE-2026-3116 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16246.

When was CVE-2026-3116 published?

CVE-2026-3116 was published on 2026-03-26 and last updated on 2026-06-17.

CVE-2026-3116

CVE-2026-3116 is a medium-severity vulnerability in Mattermost Mattermost Server with a CVSS 3.x base score of 4.9. 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-400.

Key facts

Severity: Medium (CVSS 3.x base score 4.9)
EPSS exploit prediction: 0% (26th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-16246
Weakness: CWE-400
Affected product: Mattermost Mattermost Server
Published: 2026-03-26
Last modified: 2026-06-17

Description

Mattermost Plugins versions <=11.4 11.0.4 11.1.3 11.3.2 10.11.11.0 fail to validate incoming request size which allows an authenticated attacker to cause service disruption via the webhook endpoint. Mattermost Advisory ID: MMSA-2026-00589

Frequently asked questions

What is CVE-2026-3116?: Mattermost Plugins versions <=11.4 11.0.4 11.1.3 11.3.2 10.11.11.0 fail to validate incoming request size which allows an authenticated attacker to cause service disruption via the webhook endpoint. Mattermost Advisory ID: MMSA-2026-00589
How severe is CVE-2026-3116?: CVE-2026-3116 has a CVSS 3.x base score of 4.9, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-3116 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.
What products are affected by CVE-2026-3116?: CVE-2026-3116 affects Mattermost Mattermost Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-3116?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-3116 have an EU (EUVD) identifier?: Yes. CVE-2026-3116 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16246.
When was CVE-2026-3116 published?: CVE-2026-3116 was published on 2026-03-26 and last updated on 2026-06-17.

References

https://mattermost.com/security-updates

Affected products (1)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

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