Firefox End of Life (EOL) Dates & Support Timeline

Firefox release and support pattern

Across the 57 release lines with a published release date, Firefox has shipped a new line roughly every 4 weeks (median interval). A line typically stays supported for about 4 weeks from its release to its end-of-life date (measured on the 55 lines with both dates published). 7 of the 57 tracked lines are designated long-term support, which is where the longer windows sit.

Of the 57 release lines tracked, 53 are past end of life and 4 are still within support. The newest line, 156, was released September 15, 2026. The next scheduled end of life is 140 on September 29, 2026 — 5 days from this build. The longest-supported line currently published is 115, to March 31, 2027.

Computed from the tracked release data at every build — the figures above are the dates in the table, restated, not an editorial estimate.

Firefox security intelligence

CISA KEV history: Firefox is named in CISA's Known Exploited Vulnerabilities catalog 12 times, most recently on 2024-10-15, including use in ransomware campaigns. Derived from CISA's live catalog at every build.

What does Firefox end of life mean for your organization?

When a version of Firefox reaches end of life, the maintainers stop issuing security patches. Vulnerabilities discovered after this date are publicly disclosed on the National Vulnerability Database, exploit code appears on GitHub, and your systems remain permanently exposed.

The CVE blind spot: A CVE-based scan does not show the accumulation of unpatched vulnerabilities in EOL software. Some scanners flag unsupported versions of common products, but coverage varies, and none of them give you the date in advance. With a zero-day, nobody knows about the vulnerability. With EOL software, the vulnerability is public — listed, rated, and often weaponized — but no vendor patch is coming. This is one of the most dangerous gaps in enterprise security posture.

Organizations running EOL Firefox should treat it as a vulnerability class in their risk register, apply compensating controls (network segmentation, enhanced monitoring, access restriction), and prioritize migration to a supported version.

Your options when Firefox reaches end of life

There are four realistic paths. Which one is right depends far more on how long the system needs to keep running than on the version you are on today.

How to choose, in one question: how many more years does this system need to run? Under a year, extended support (where it exists) is usually cheaper than an emergency migration. One to three years, migrate — support purchased repeatedly costs more than doing the project once, and the project only gets harder as the version ages. Indefinitely, migrate now and plan the next migration before it surprises you.

Worth saying plainly, because vendors selling extended support rarely will: extended support is often the more expensive choice over a multi-year horizon. It is the right answer when a deadline is genuinely unreachable, not as a default. Compare the annual fee against the one-time cost of migrating before committing to either.

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