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MEDIUM severity

Mattermost Server doesn't limit the number of user preferencesGHSA-mcw6-3256-64gg

MEDIUMFix: mattermost/mattermost@11a21f4

GHSA-mcw6-3256-64gg is a medium-severity (CVSS 4.3) Uncontrolled Resource Consumption vulnerability in github.com/mattermost/mattermost/server/v8. A fix is available for github.com/mattermost/mattermost/server/v8 — see the affected versions and patch details below.

Also known asBIT-mattermost-2024-28949CVE-2024-28949GO-2024-2695
Published
Updated
Affected
4 pkgs
Patched
4 / 4
Exploits
None indexed
Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-mcw6-3256-64gg.

EPSS Exploitation Probability

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs47th percentile — riskier than 47% of all scored CVEsHighest risk
0.00%0.35%0.71%1.06%0.1%0.6%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

4 pkgs affected
🐹github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost/server/v8

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Mattermost Server versions 9.5.x before 9.5.2, 9.4.x before 9.4.4, 9.3.x before 9.3.3, 8.1.x before 8.1.11 don't limit the number of user preferences which allows an attacker to send a large number of user preferences potentially causing denial of service.

Affected Packages

4 total 4 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/mattermost/mattermost/server/v8≥ 8.1.0&&< 8.1.118.1.11go get github.com/mattermost/mattermost/server/v8@v8.1.11
🐹Gogithub.com/mattermost/mattermost/server/v8≥ 9.3.0&&< 9.3.39.3.3go get github.com/mattermost/mattermost/server/v8@v9.3.3
🐹Gogithub.com/mattermost/mattermost/server/v8≥ 9.4.0&&< 9.4.49.4.4go get github.com/mattermost/mattermost/server/v8@v9.4.4
🐹Gogithub.com/mattermost/mattermost/server/v8≥ 9.5.0&&< 9.5.29.5.2go get github.com/mattermost/mattermost/server/v8@v9.5.2

Affected Products

1 product · 4 configurations
Application
mattermost servermattermost
≥ 9.5.0 && < 9.5.2
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/mattermost/mattermost/server/v8, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/mattermost/mattermost/server/v8 to 8.1.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mcw6-3256-64gg is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

Mattermost Server versions 9.5.x before 9.5.2, 9.4.x before 9.4.4, 9.3.x before 9.3.3, 8.1.x before 8.1.11 don't limit the number of user preferences which allows an attacker to send a large number of user preferences potentially causing denial of service.
O3 Security · Impact-Aware SCA

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