Memory Exhaustion via Malicious 7zip File Upload
Summary
| CVE | CVE-2026-6340 |
|---|---|
| State | PUBLISHED |
| Assigner | Mattermost |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-18 08:16:14 UTC |
| Updated | 2026-05-19 17:21:26 UTC |
| 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 |
Risk And Classification
Primary CVSS: v3.1 6.5 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.000470000 probability, percentile 0.144850000 (date 2026-05-26)
Problem Types: CWE-789 | CWE-789 CWE-789: Memory Allocation with Excessive Size Value
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | [email protected] | Secondary | 4.3 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L |
| 3.1 | CNA | CVSS | 4.3 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Mattermost | Mattermost Server | All | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Mattermost | Mattermost | affected 11.5.0 11.5.1 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 10.11.0 10.11.13 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.4.0 11.4.3 semver | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.6.0 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.5.2 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 10.11.14 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.4.4 | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| mattermost.com/security-updates | [email protected] | mattermost.com | Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Juho Forsén (en)
Additional Advisory Data
Solutions
CNA: Update Mattermost to versions 11.6.0, 11.5.2, 10.11.14, 11.4.4 or higher.
There are currently no legacy QID mappings associated with this CVE.