CVE-2022-3257 Server-side Denial of Service while processing a specifically crafted GIF file

What is CVE-2022-3257?

CVE-2022-3257 is a low-severity denial of service vulnerability in Mattermost Mattermost Server, published on 23 Sep 2022. Any signed-in user can exploit it over the network, with no action from the victim.

Official 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.

Weakness: CWE-434, CWE-400

Which versions are affected by CVE-2022-3257?

3 open source packages ship an affected version, including github.com/mattermost/mattermost-server/v6 and mattermost. It affects 1 product.

Products include Mattermost Mattermost Server.

How do I fix CVE-2022-3257?

Upgrade github.com/mattermost/mattermost-server/v6 to 7.2.0 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2022-3257 being exploited?

There is no known exploitation of CVE-2022-3257 in the wild and no public exploit code.

Other vulnerabilities in Mattermost Mattermost Server

• CVE-2025-12419 Account takeover on OAuth/OpenID-enabled servers Critical 9.9
• CVE-2025-12421 Account Takeover via Code Exchange Endpoint Critical 9.9
• CVE-2025-4981 Path Traversal Leading to RCE by Any Authenticated Mattermost User Critical 9.9
• CVE-2025-20051 Arbitrary file read via block duplication in Mattermost Boards Critical 9.9
• CVE-2025-25279 Arbitrary file read in Mattermost Boards via import & export board archive Critical 9.9

All Mattermost Mattermost Server vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-mattermost-2022-3257, GHSA-m7w4-q5vg-5xfp.