CVE-2026-3114: Zip Bomb Denial of Service via Unrestricted Archive Decompression

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-26 · updated 2026-06-17
Weakness: CWE-409

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

Affected products

Mattermost: from 10.11.0 before 10.11.12; from 11.2.0 before 11.2.4; from 11.3.0 before 11.3.2; 11.4.0 — fixed in 10.11.12, 11.2.4, 11.3.2

How to fix

Upgrade to a fixed version: Mattermost 10.11.12, 11.2.4, 11.3.2. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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