CVE-2026-6340
Memory Exhaustion in Mattermost via Malicious 7zip Archive
Publication date: 2026-05-18
Last updated on: 2026-05-19
Assigner: Mattermost, Inc.
Description
Description
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| mattermost | mattermost_server | From 10.11.0 (inc) to 10.11.14 (exc) |
| mattermost | mattermost_server | From 11.4.0 (inc) to 11.4.4 (exc) |
| mattermost | mattermost_server | From 11.5.0 (inc) to 11.5.2 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-789 | The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability affects certain versions of Mattermost (11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3) where the software fails to properly validate the structure of 7zip archives before processing them.
An authenticated attacker can exploit this by uploading a specially crafted 7zip file that contains excessive folder declarations, which causes the server to exhaust its memory resources.
This leads to a denial of service condition on the server.
How can this vulnerability impact me? :
The primary impact of this vulnerability is a denial of service (DoS) on the Mattermost server.
By uploading a malicious 7zip file with excessive folder declarations, an authenticated attacker can cause the server to exhaust its memory, potentially making the service unavailable to legitimate users.
This can disrupt communication and collaboration within an organization relying on Mattermost.
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, you should upgrade Mattermost to a version later than the affected versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, and 11.4.x <= 11.4.3 where the issue with 7zip archive validation has been fixed.
Additionally, monitor Mattermost's official security updates page and subscribe to their security bulletin for notifications about fixes and patches.