Mattermost versions <=11.9 11.0.9 11.4.8 11.7.7 10.22.11.0 fail to recover from handler panics, which allows an authenticated user to crash the plugin via a post-action request with an unexpected field type.. Mattermost Advisory ID: MMSA-2026-00701

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact Low

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Exploitation none

Automatable no

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Mattermost Mattermost unaffected
Version Status Constraints
<=11.9 11.0.9 11.4.8 11.7.7 10.22.11.0 affected ≤ <=11.9 11.0.9 11.4.8 11.7.7 10.22.11.0
11.10.0 unaffected —
11.9.1 unaffected —
11.8.5 unaffected —
11.7.8 unaffected —
10.11.23 unaffected —

No data.

No data.

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Vendors Products
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Project Subscriptions

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Advisories

No advisories yet.

Fixes

Solution

Update Mattermost to versions 11.10.0, 11.9.1, 11.8.5, 11.7.8, 10.11.23 or higher.

Workaround

No workaround given by the vendor.

References
Link Providers
https://mattermost.com/security-updates cve-icon cve-icon
History

Mon, 14 Sep 2026 21:00:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Mon, 14 Sep 2026 14:00:00 +0000

Type Values Removed Values Added
Description Mattermost versions <=11.9 11.0.9 11.4.8 11.7.7 10.22.11.0 fail to recover from handler panics, which allows an authenticated user to crash the plugin via a post-action request with an unexpected field type.. Mattermost Advisory ID: MMSA-2026-00701
Title MS Calendar plugin: unrecovered handler panics from malformed post-action requests could crash the plugin process
Weaknesses CWE-704
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-09-14T19:23:01.298Z

Reserved: 2026-09-07T09:35:28.446Z

Link: CVE-2026-86348

cve-icon Vulnrichment

Updated: 2026-09-14T19:15:28.648Z

cve-icon NVD

Status : Received

Published: 2026-09-14T14:17:15.570

Modified: 2026-09-14T20:17:00.760

Link: CVE-2026-86348

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-14T20:15:06Z

Weaknesses