Question 1

What is the EOL Risk Score for Mattermost 11.9?

Accepted Answer

Mattermost 11.9 has an EOL Risk Score™ of 25 out of 100, placing it in the Low risk band. The score is calculated from four factors: EOL Recency (15/40), Attack Surface (10/30), CISA KEV Exposure (0/20), and Extended Support Availability (0/10).

Question 2

Is Mattermost 11.9 still supported?

Accepted Answer

Mattermost 11.9 is currently supported. End of life is scheduled for October 15, 2026. Plan your migration before that date to avoid security risk.

Question 3

When does Mattermost 11.9 reach end of life?

Accepted Answer

Mattermost 11.9 reached (or will reach) end of life on October 15, 2026. After this date, no security patches or bug fixes are issued by the vendor.

Question 4

What are the security risks of running Mattermost 11.9 after end of life?

Accepted Answer

After end of life, Mattermost 11.9 no longer receives security patches. Any newly discovered CVEs remain unpatched indefinitely. Organizations running EOL software also face compliance violations under SOC 2, PCI DSS, HIPAA, and ISO 27001, which require use of supported software versions.