CVE-2026-25783
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User-Agent Header Validation Flaw Causes Panic in Mattermost
Vulnerability report for CVE-2026-25783, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-03-16
Last updated on: 2026-03-18
Assigner: Mattermost, Inc.
Description
Description
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate User-Agent header tokens which allows an authenticated attacker to cause a request panic via a specially crafted User-Agent header. Mattermost Advisory ID: MMSA-2026-00586
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| mattermost | mattermost_server | From 10.11.0 (inc) to 10.11.11 (exc) |
| mattermost | mattermost_server | From 11.2.0 (inc) to 11.2.3 (exc) |
| mattermost | mattermost_server | From 11.3.0 (inc) to 11.3.1 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-1287 | The product receives input that is expected to be of a certain type, but it does not validate or incorrectly validates that the input is actually of the expected type. |
