CVE-2026-6340
Mattermost doesn't validate 7zip archive structure before processing in github.com/mattermost/mattermost-server
Description
Mattermost doesn't validate 7zip archive structure before processing in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: github.com/mattermost/mattermost-server/v5 before v5.3.2-0.20260325191733-fb11968f8798.
How to fix CVE-2026-6340
To remediate CVE-2026-6340, upgrade the affected package to a fixed version below.
- —upgrade to 5.3.2-0.20260325191733-fb11968f8798 or later
- —upgrade to 10.11.14+incompatible or later
- —no fix listed
- —no fix listed
- —upgrade to 11.5.2 or later
- —upgrade to 8.0.0-20260325191733-fb11968f8798 or later
Is CVE-2026-6340 being exploited?
Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.
Affected packages (6)
- from 0, < 5.3.2-0.20260325191733-fb11968f8798
- >= 10.11.0+incompatible, < 10.11.14+incompatible, >= 11.4.0+incompatible, < 11.4.4+incompatible, >= 11.5.0+incompatible, < 11.5.2+incompatible
- from 0
- from 0
- >= 11.5.0, < 11.5.2
- from 0, < 8.0.0-20260325191733-fb11968f8798
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM4.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L |