Mattermost doesn't limit the size of the request body on the start meeting API endpoint

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-2325: 0.24% estimated exploitation activity in the next 30 days; percentile 15.18 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to limit the size of the request body on the start meeting API endpoint, which allows an authenticated attacker to cause resource exhaustion or denial of service via a crafted oversized HTTP POST request to {{/api/v1/meetings}}.. Mattermost Advisory ID: MMSA-2026-00608

Published by the source

18 May 2026, 09:31 UTC

Last modified by the source

1 Jun 2026, 15:51 UTC

Source last checked

26 Oct 2026, 15:23 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-m3p3-8frq-q7qh

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-2325

Advisory: Mattermost doesn't limit the size of the request body on the start meeting API endpoint
IDs: CVE-2026-2325, GHSA-m3p3-8frq-q7qh
Record: https://patchnext.com/advisories/cve-2026-2325 (revision 1, source checked 26 Oct 2026, 15:23 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/mattermost/mattermost-server 11.5.2, 11.4.4, 10.11.14; github.com/mattermost/mattermost-plugin-msteams-meetings 1.1.1-0.20260213105619-c5892dd169de. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/mattermost/mattermost-server: affected >= 11.5.0, < 11.5.2; >= 10.11.0, < 10.11.14; >= 11.4.0, < 11.4.4; fixed in 11.4.4, 10.11.14, 11.5.2
- Go github.com/mattermost/mattermost-plugin-msteams-meetings: affected < 1.1.1-0.20260213105619-c5892dd169de; fixed in 1.1.1-0.20260213105619-c5892dd169de

## Suggested inspection (read-only)
- Go github.com/mattermost/mattermost-server: check the installed version with your package manager.
- Go github.com/mattermost/mattermost-plugin-msteams-meetings: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-plugin-msteams-meetings.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-m3p3-8frq-q7qh (GitHub-reviewed advisory GHSA-m3p3-8frq-q7qh lists affected ranges: Go github.com/mattermost/mattermost-server >=11.5.0 =10.11.0 =11.4.0 =0 <1.1.1-0.20260213105619-c5892dd169de)

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