CVE-2025-20033: mattermost server — Fix

Description

Mattermost versions 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly validate post types, which allows attackers to deny service to users with the sysconsole_read_plugins permission via creating a post with the custom_pl_notification type and specific props.

Is your site exposed to CVE-2025-20033?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

4.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

Weakness Type (CWE)

CWE-1287 CWE-1287

Affected Products

Vendor	Product	Versions
mattermost	mattermost_server	9.11.0 — 9.11.6
mattermost	mattermost_server	10.0.0 — 10.0.4
mattermost	mattermost_server	10.1.0 — 10.1.4
mattermost	mattermost_server	10.2.0 — 10.2.1

References

Advisories & Patches

https://mattermost.com/security-updates

Frequently Asked Questions

What is CVE-2025-20033? +

Mattermost versions 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly validate post types, which allows attackers to deny service to users with the sysconsole_read_plugins permission via creating a post with the custom_pl_notification type and specific props. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2025-20033? +

CVE-2025-20033 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-20033? +

CVE-2025-20033 affects products from mattermost, specifically: mattermost_server. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-20033? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-102714

`_nx_icmpv6_validate_options()` scans the option area with `while (length > 2)` (`common/src/nx_icmpv6_validate_options.c:79`). An area whose size leaves a one- or two-byte …

CVE-2026-80051

github.com/graphql-go/graphql (GraphQL for Go) through 0.8.1 does not validate that a scalar variable value matches its declared type. The built-in …

CVE-2026-10825

A denial-of-service vulnerability exists in the WebSocket API due to insufficient validation and handling of JSON-based requests. A low-privileged authenticated …

CVE-2025-9041

A security issue exists due to improper handling of CIP Class 32’s request when a module is inhibited on the …

CVE-2025-9042

A security issue exists due to improper handling of CIP Class 32’s request when a module is inhibited on the …

CVE-2026-82741

Improper Validation of Specified Type of Input vulnerability in ash-project ash lets an attacker confuse the stored type tag of …

CVE-2025-20033