CVE-2017-18920

Name: CVE-2017-18920
Creator: NVD / NIST
Published: 2020-06-19T20:15:12.71+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.24%

Last modified Jun 17, 2026

CVE-2017-18920 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. An issue was discovered in Mattermost Server before 3.6.2. The WebSocket feature does not follow the Same Origin Policy.. EPSS estimates a 1.24% chance of exploitation in the next 30 days.

Description

An issue was discovered in Mattermost Server before 3.6.2. The WebSocket feature does not follow the Same Origin Policy.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

1.24%

65.4th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Mattermost	Mattermost Server	< 3.6.2

References

https://mattermost.com/security-updates/Vendor Advisory
https://mattermost.com/security-updates/Vendor Advisory

Timeline

Published: Jun 19, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2017-18920?

An issue was discovered in Mattermost Server before 3.6.2. The WebSocket feature does not follow the Same Origin Policy.

How severe is CVE-2017-18920?

CVE-2017-18920 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.24% probability of exploitation in the next 30 days.

How do I fix CVE-2017-18920?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2017-18920?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST