What is CVE-2018-21260?

CVE-2018-21260 is a low-severity vulnerability in Mattermost Server, classified under Information Disclosure. CVSS score: 2.7/10. Published 2020-06-19.

How severe is CVE-2018-21260?

Low severity. CVSS v3 base score is 2.7 out of 10.

Information disclosure in Mattermost Server

CVE-2018-21260

An issue was discovered in Mattermost Server before 4.8.1, 4.7.4, and 4.6.3. WebSocket events were accidentally sent during certain user-management operations, violating user privacy.

Vulnerability class: Information Disclosure

Published 2020-06-19 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 2.7 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.007 (52.7th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 52.7% 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 Server

Weakness classification (CWE)

CWE-200 — Information Disclosure

References

mattermost.com/security-updates/ (Vendor Advisory)

Frequently asked questions

What is CVE-2018-21260?: CVE-2018-21260 is a low-severity vulnerability in Mattermost Server, classified under Information Disclosure. CVSS score: 2.7/10. Published 2020-06-19.
How severe is CVE-2018-21260?: Low severity. CVSS v3 base score is 2.7 out of 10.