Question 1

What is the EOL Risk Score for Cisco IOS 15.5(3)M?

Accepted Answer

Cisco IOS 15.5(3)M has an EOL Risk Score™ of 70 out of 100, placing it in the High risk band. The score is calculated from four factors: EOL Recency (40/40), Attack Surface (10/30), CISA KEV Exposure (20/20), and Extended Support Availability (0/10).

Question 2

Is Cisco IOS 15.5(3)M still supported?

Accepted Answer

Cisco IOS 15.5(3)M is no longer supported — it has passed its end of life date (June 4, 2020). No further security patches will be issued. Upgrade to a supported version or obtain extended lifecycle support.

Question 3

When does Cisco IOS 15.5(3)M reach end of life?

Accepted Answer

Cisco IOS 15.5(3)M reached (or will reach) end of life on June 4, 2020. After this date, no security patches or bug fixes are issued by the vendor.

Question 4

What are the security risks of running Cisco IOS 15.5(3)M after end of life?

Accepted Answer

After end of life, Cisco IOS 15.5(3)M 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.