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MEDIUM severity

Mattermost denial of service through long emoji valueGHSA-6mx3-9qfh-77gj

MEDIUM

GHSA-6mx3-9qfh-77gj 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-2024-24988CVE-2024-24988GO-2024-2589
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Nov 7, 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-6mx3-9qfh-77gj.

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs53th percentile — riskier than 53% of all scored CVEsHighest risk
0.00%0.39%0.79%1.18%0.4%0.7%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

2 pkgs affected
🐹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 fails to properly validate the length of the emoji value in the custom user status, allowing an attacker to send multiple times a very long string as an emoji value causing high resource consumption and possibly crashing the server.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/mattermost/mattermost/server/v8≥ 9.3.0&&< 9.3.19.3.1go get github.com/mattermost/mattermost/server/v8@v9.3.1
🐹Gogithub.com/mattermost/mattermost/server/v8≥ 9.2.0&&< 9.2.59.2.5go get github.com/mattermost/mattermost/server/v8@v9.2.5

Affected Products

1 product · 3 configurations
Application
mattermost servermattermost
≥ 9.2.0 && < 9.2.4
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 9.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6mx3-9qfh-77gj 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 fails to properly validate the length of the emoji value in the custom user status, allowing an attacker to send multiple times a very long string as an emoji value causing high resource consumption and possibly crashing the server.
O3 Security · Impact-Aware SCA

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Mattermost denial of service through long emoji value