CVE-2026-6340

medium

Published 2026-05-18 · Modified 2026-05-19

CVSS v3

6.5

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS v2

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VIR risk

6.5

Description

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate 7zip archive structure before processing which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted 7zip file with excessive folder declarations.. Mattermost Advisory ID: MMSA-2026-00573

Predictions

Exploit likelihood

75%

Patch ETA

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Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: responsibledisclosure@mattermost.com — https://mattermost.com/security-updates

Application impact

Vendor	Product	Versions	Fixed
mattermost	mattermost_server	`{"startIncluding":"10.11.0","endExcluding":"10.11.14"}`	`10.11.14`

References

https://mattermost.com/security-updates

CWEs

CWE-789

Verify integrity in audit chain (admin only). AS-IS.