How severe is CVE-2026-3114?

CVE-2026-3114 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-3114 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (28th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-3114?

CVE-2026-3114 primarily affects Mattermost Mattermost Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-3114?

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

Does CVE-2026-3114 have an EU (EUVD) identifier?

Yes. CVE-2026-3114 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16242.

When was CVE-2026-3114 published?

CVE-2026-3114 was published on 2026-03-26 and last updated on 2026-06-17.

CVE-2026-3114

CVE-2026-3114 is a medium-severity vulnerability in Mattermost Mattermost Server 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-409.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (28th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-16242
Weakness: CWE-409
Affected product: Mattermost Mattermost Server
Published: 2026-03-26
Last modified: 2026-06-17

Description

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to validate decompressed archive entry sizes during file extraction which allows authenticated users with file upload permissions to cause a denial of service via crafted zip archives containing highly compressed entries (zip bombs) that exhaust server memory.. Mattermost Advisory ID: MMSA-2026-00598

Frequently asked questions

What is CVE-2026-3114?: Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to validate decompressed archive entry sizes during file extraction which allows authenticated users with file upload permissions to cause a denial of service via crafted zip archives containing highly compressed entries (zip bombs) that exhaust server memory.. Mattermost Advisory ID: MMSA-2026-00598
How severe is CVE-2026-3114?: CVE-2026-3114 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-3114 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (28th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-3114?: CVE-2026-3114 primarily affects Mattermost Mattermost Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-3114?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-3114 have an EU (EUVD) identifier?: Yes. CVE-2026-3114 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16242.
When was CVE-2026-3114 published?: CVE-2026-3114 was published on 2026-03-26 and last updated on 2026-06-17.

References

https://mattermost.com/security-updates

Affected products (2)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_server:11.4.0:*:*:*:*:*:*:*

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