What is CVE-2021-37866?

CVE-2021-37866 is a medium-severity vulnerability in Mattermost Boards, classified under Insufficient Session Expiration. CVSS score: 4.7/10. Published 2022-01-18.

How severe is CVE-2021-37866?

Medium severity. CVSS v3 base score is 4.7 out of 10.

Vulnerability in Mattermost Boards

CVE-2021-37866

Mattermost Boards plugin v0.10.0 and earlier fails to invalidate a session on the server-side when a user logged out of Boards, which allows an attacker to reuse old session token for authorization.

Published 2022-01-18 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.7 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.007 (52.2th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 52nd percentile — 52.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Mattermost Boards — versions unspecified, 0.9.5, 0.8.4
Mattermost Boards

Weakness classification (CWE)

CWE-613 — Insufficient Session Expiration

References

mattermost.com/security-updates/ (Vendor Advisory)
www.whitesourcesoftware.com/vulnerability-database/CVE-2021-37866 (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2021-37866?: CVE-2021-37866 is a medium-severity vulnerability in Mattermost Boards, classified under Insufficient Session Expiration. CVSS score: 4.7/10. Published 2022-01-18.
How severe is CVE-2021-37866?: Medium severity. CVSS v3 base score is 4.7 out of 10.