What is CVE-2021-37863?

CVE-2021-37863 is a low-severity vulnerability in Mattermost, classified under Improper Input Validation. CVSS score: 3.5/10. Published 2021-12-17.

How severe is CVE-2021-37863?

Low severity. CVSS v3 base score is 3.5 out of 10.

Improper input validation in Mattermost

CVE-2021-37863

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.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2021-12-17 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 3.5 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.008 (56.0th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 56th percentile — 56.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Mattermost — versions unspecified
Mattermost Server

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

mattermost.com/security-updates/ (Vendor Advisory)
hackerone.com/reports/1253732 (Permissions Required)

Frequently asked questions

What is CVE-2021-37863?: CVE-2021-37863 is a low-severity vulnerability in Mattermost, classified under Improper Input Validation. CVSS score: 3.5/10. Published 2021-12-17.
How severe is CVE-2021-37863?: Low severity. CVSS v3 base score is 3.5 out of 10.