CVE-2026-5740
Analyzed
Analyzed - Analysis Complete
BaseFortify
Vulnerability report for CVE-2026-5740, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-05-22
Last updated on: 2026-05-22
Assigner: Mattermost, Inc.
Description
Description
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to properly validate msgpack-encoded WebSocket frames before memory allocation which allows an unauthenticated remote attacker to crash the server process and cause a full service outage for all users via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID: MMSA-2026-00647
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| mattermost | mattermost_server | From 10.11.0 (inc) to 10.11.15 (exc) |
| mattermost | mattermost_server | From 11.4.0 (inc) to 11.4.5 (exc) |
| mattermost | mattermost_server | From 11.5.0 (inc) to 11.5.4 (exc) |
| mattermost | mattermost_server | From 11.6.0 (inc) to 11.6.1 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| 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. |
