Cisco IOS 12.4 Mainline · Version Status
Cisco IOS 12.4 Mainline End of Life Date
Cisco IOS 12.4 Mainline end-of-life date, support status, and CVE risk. Dates read at the vendor's own lifecycle pages (cisco.com); the source of each date is on the product page.
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Cisco IOS 12.4 Mainline is past end of life. This version no longer receives security patches. Past EOL — migrate to a supported version immediately.
EOL Date
date not published
Past EOL
Latest Release
12.4
Standard release
Release Date
—
Cisco IOS 12.4 Mainline series
Extended Support
Jan 31, 2016
Extended support · ended
Attack Surface
10/30 Medium tier
CISA KEV Exposure
20/20 Named in CISA KEV
Extended Support
0/10 Available
EOL Risk Score™ — proprietary methodology by endoflife.ai. Factors: EOL recency, attack surface breadth, CISA KEV catalog presence, extended support availability. Updated at every build.
Methodology → ·
View score card →
Extended Support
Extended Cisco IOS 12.4 Mainline support is available
Commercial vendors offer security patches beyond EOL. Compare your options.
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What does Cisco IOS 12.4 Mainline end of life mean?
When Cisco IOS 12.4 Mainline reaches end of life, the maintainers stop issuing security patches for this version. CVEs discovered after the EOL date are publicly disclosed on the National Vulnerability Database with no patch available. Exploit code frequently appears on GitHub within days of disclosure.
The CVE blind spot: A CVE-based scan does not show the ongoing accumulation of unpatched vulnerabilities in EOL software versions. Some scanners flag unsupported versions of common products, but coverage varies, and none of them give you the date in advance. Running Cisco IOS 12.4 Mainline past its EOL date creates a growing attack surface that a clean scan result does not rule out.
Migrate to Cisco IOS 15.9(3)M or implement compensating controls — network segmentation, enhanced monitoring, restricted access — while migration is underway.
Frequently Asked Questions
When does Cisco IOS 12.4 Mainline reach end of life?
Cisco IOS 12.4 Mainline has already reached end of life, though the vendor has not published an exact date.
Is Cisco IOS 12.4 Mainline still supported?
No. Cisco IOS 12.4 Mainline reached end of life on date not published and is no longer receiving security patches.
What should I upgrade to from Cisco IOS 12.4 Mainline?
The recommended upgrade from Cisco IOS 12.4 Mainline is
Cisco IOS 15.9(3)M — the latest actively supported version. Check the
Cisco IOS full timeline for all supported versions.
What are the security risks of running Cisco IOS 12.4 Mainline past EOL?
When Cisco IOS 12.4 Mainline reaches end of life, the maintainers stop issuing security patches. Any CVEs disclosed after the EOL date accumulate with no vendor fix. A CVE-based scan does not show this — it is the CVE blind spot; some scanners flag unsupported versions of common products, but coverage varies and none give the date in advance. Organizations running EOL Cisco IOS should migrate immediately or implement compensating controls.