CVE-2021-37863 Denial of service in Mattermost
Authenticated attackers can crash the Mattermost web client by submitting a maliciously crafted post due to insufficient parameter validation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2021-37863?
CVE-2021-37863 is a low-severity denial of service vulnerability in Mattermost Mattermost Server, published on 17 Dec 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Mattermost 6.0 and earlier fails to sufficiently validate parameters during post creation, which allows authenticated attackers to cause a client-side crash of the web application via a maliciously crafted post.
Weakness: CWE-20
Which versions are affected by CVE-2021-37863?
1 open source package ship an affected version, including mattermost. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
mattermost Bitnami | All versions | 6.0.1 |
Products include Mattermost Mattermost Server.
How do I fix CVE-2021-37863?
Upgrade mattermost to 6.0.1 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-2021-37863 being exploited?
There is no known exploitation of CVE-2021-37863 in the wild and no public exploit code.
Other vulnerabilities in Mattermost Mattermost Server
- CVE-2025-12419 Account takeover on OAuth/OpenID-enabled servers
- CVE-2025-12421 Account Takeover via Code Exchange Endpoint
- CVE-2025-4981 Path Traversal Leading to RCE by Any Authenticated Mattermost User
- CVE-2025-20051 Arbitrary file read via block duplication in Mattermost Boards
- CVE-2025-25279 Arbitrary file read in Mattermost Boards via import & export board archive
Sources
Also known as BIT-mattermost-2021-37863, GHSA-7523-wx28-g6xf.