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CVE Vulnerability Details :
CVE-2026-6340
PUBLISHED
More InfoOfficial Page
Assigner-Mattermost
Assigner Org ID-9302f53e-dde5-4bf3-b2f2-a83f91ac0eee
View Known Exploited Vulnerability (KEV) details
Published At-18 May, 2026 | 07:08
Updated At-18 May, 2026 | 12:43
Rejected At-
▼CVE Numbering Authority (CNA)
Memory Exhaustion via Malicious 7zip File Upload

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

Affected Products
Vendor
Mattermost, Inc.Mattermost
Product
Mattermost
Default Status
unaffected
Versions
Affected
  • From 11.5.0 through 11.5.1 (semver)
  • From 10.11.0 through 10.11.13 (semver)
  • From 11.4.0 through 11.4.3 (semver)
Unaffected
  • 11.6.0
  • 11.5.2
  • 10.11.14
  • 11.4.4
Problem Types
TypeCWE IDDescription
CWECWE-789CWE-789: Memory Allocation with Excessive Size Value
Type: CWE
CWE ID: CWE-789
Description: CWE-789: Memory Allocation with Excessive Size Value
Metrics
VersionBase scoreBase severityVector
3.14.3MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Version: 3.1
Base score: 4.3
Base severity: MEDIUM
Vector:
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Update Mattermost to versions 11.6.0, 11.5.2, 10.11.14, 11.4.4 or higher.

Configurations
Workarounds
Exploits
Credits
finder
Juho Forsén
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
https://mattermost.com/security-updates
vendor-advisory
Hyperlink: https://mattermost.com/security-updates
Resource:
vendor-advisory
▼Authorized Data Publishers (ADP)
CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
Details not found