What is CVE-2026-8683?

CVE-2026-8683 is a medium-severity vulnerability in Mattermost, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 6.5/10. Published 2026-06-15.

How severe is CVE-2026-8683?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Resource exhaustion in Mattermost

CVE-2026-8683

Mattermost Desktop App versions <=6.1 5.5.13.0 fail to account for attempting to open extremely long URLs in the Mattermost Desktop App which allows a malicious server owner to crash the application via including a script to call window.open on a very large URL. Mattermost Advisory ID: MMSA-2026-00652

Published 2026-06-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.004 (26.7th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 27th percentile — 26.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002

Affected products

Mattermost — versions 0, 6.2.0, 5.13.6.0
Mattermost Desktop

Weakness classification (CWE)

CWE-770 — Allocation of Resources Without Limits or Throttling

References

mattermost.com/security-updates (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-8683?: CVE-2026-8683 is a medium-severity vulnerability in Mattermost, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 6.5/10. Published 2026-06-15.
How severe is CVE-2026-8683?: Medium severity. CVSS v3 base score is 6.5 out of 10.