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MEDIUM severity

Mattermost subject to Denial of Service via upload of special GIFGHSA-m7w4-q5vg-5xfp

MEDIUM

GHSA-m7w4-q5vg-5xfp is a medium-severity (CVSS 6.5) Uncontrolled Resource Consumption vulnerability in github.com/mattermost/mattermost-server/v6. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for github.com/mattermost/mattermost-server/v6 — see the affected versions and patch details below.

Also known asBIT-mattermost-2022-3257CVE-2022-3257
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Nov 10, 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-m7w4-q5vg-5xfp.

EPSS Exploitation Probability

via FIRST.org ↗
1.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs70th percentile — riskier than 70% of all scored CVEsHighest risk
0.00%0.59%1.17%1.76%0.4%0.4%1.1%1.3%1.3%May 26Jul 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

1 pkg affected
🐹github.com/mattermost/mattermost-server/v6

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 version 7.1.x and earlier fails to sufficiently process a specifically crafted GIF file when it is uploaded while drafting a post, which allows authenticated users to cause resource exhaustion while processing the file, resulting in server-side Denial of Service.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/mattermost/mattermost-server/v6≥ 7.1.0&&< 7.2.07.2.0go get github.com/mattermost/mattermost-server/v6@v7.2.0

Affected Products

1 product · 1 configurations
Application
mattermost servermattermost
< 7.2.0
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Mattermost version 7.1.x and earlier fails to sufficiently process a spe…

hackerone.comNVDSep 2022

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/v6, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/mattermost/mattermost-server/v6 to 7.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-m7w4-q5vg-5xfp is resolved across your whole dependency graph.

  3. Workarounds

    Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.

Frequently Asked Questions

Mattermost version 7.1.x and earlier fails to sufficiently process a specifically crafted GIF file when it is uploaded while drafting a post, which allows authenticated users to cause resource exhaustion while processing the file, resulting in server-side Denial of Service.
O3 Security · Impact-Aware SCA

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Mattermost subject to Denial of Service via upload of…