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Mattermost doesn't validate decompressed archive entry sizes during file extraction

Moderate severity GitHub Reviewed Published Mar 26, 2026 to the GitHub Advisory Database • Updated Mar 31, 2026

Package

gomod github.com/mattermost/mattermost/server/v8 (Go)

Affected versions

= 11.4.0
>= 11.3.0, < 11.3.2
>= 11.2.0, < 11.2.4
>= 10.11.0, < 10.11.12
>= 8.0.0-20260105080200-d27a2195068d, < 8.0.0-20260217110922-b7d4a1f1f59b

Patched versions

11.4.1
11.3.2
11.2.4
10.11.12
8.0.0-20260217110922-b7d4a1f1f59b

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.

References

Published by the National Vulnerability Database Mar 26, 2026
Published to the GitHub Advisory Database Mar 26, 2026
Reviewed Mar 31, 2026
Last updated Mar 31, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(27th percentile)

Weaknesses

Improper Handling of Highly Compressed Data (Data Amplification)

The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output. Learn more on MITRE.

CVE ID

CVE-2026-3114

GHSA ID

GHSA-vhgh-g7x8-4rx8

Source code

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