Mattermost 10.11 ended August 15, 2026 —
and the newest release is the wrong upgrade.
Mattermost 10.11 reached end of life on 15 August 2026. If you still run it, security patches have already stopped.
The instinct at that point is to upgrade to the newest release. For Mattermost that instinct is wrong, and the dates show why: the newest release, 12.0, expires on January 15, 2027, while a version released five months earlier runs until May 15, 2027. Getting this backwards means doing the upgrade work twice within a few months.
What actually stops on August 15
Mattermost 10.11 was released on 15 August 2025 and reaches end of life exactly twelve months later. Its final patch release was 10.11.23 — twenty-three patches over that year, which is a fair signal of how much security maintenance a supported Mattermost line actually receives.
After August 15, 2026 that stopped. The installation keeps running; what ends is the flow of fixes into it. Mattermost is self-hosted for most teams, which means an unpatched server sitting on your own infrastructure, usually holding the internal conversations of the entire company.
The three-month rule, and the two exceptions
Mattermost releases monthly, and the support window is short. Measured across all 58 releases tracked as of this update:
| Support window | Releases | What it means |
|---|---|---|
| 3 months | 45 | The standard. Roughly one release of overlap. 12.0 is the newest of them. |
| 4 months | 4 | Minor schedule slippage. |
| 9–10 months | 7 | Older, longer-cadence releases. |
| 12 months | 2 | The only two releases ever given a full year — 10.11 and 11.7. |
Two releases out of fifty-eight. That is the entire set of Mattermost versions that ever received a year of support, and one of the two died on August 15, 2026. The 11.10 release that shipped the day before it did not change that, and neither did 11.11 a month later or the 12.0 major release in October: all three got the standard three months.
This is why 10.11 is the version so many self-hosted teams are on. It was the sensible choice a year ago, for exactly the right reason: it was the one with a long runway. That runway ended on August 15, 2026.
The LTS label points at the wrong versions
Mattermost marks certain releases as Extended Support Releases, and our lifecycle data carries a long-term-support flag. Nine releases have it: 11.7 and 10.11, which Mattermost's own release page labels Extended, and seven older ones from the community dataset: 10.5, 9.11, 8.1, 7.8, 7.5, 7.1 and 6.3.
Every one of those seven older flagged releases is already end-of-life, the most recent having expired in November 2025; only 11.7 (and 10.11, which ended in August 2026) carries the flag with a twelve-month window behind it.
| Group | Releases | Typical window | Status today |
|---|---|---|---|
| Flagged long-term-support | 9 | 3 to 12 months | One supported (11.7), eight end-of-life |
| Not flagged, but given 12 months | 2 | 12 months | 10.11 ended August 15, 2026; 11.7 runs to May 2027 |
So the label and the longest support windows have come apart. One flagged release, 7.5, ran for barely three months. The marker alone does not tell you which window is longest: 11.7 and 10.11 carry it with twelve months behind them, 7.5 carried it with barely three, so pick your target by its end-of-life date.
Pick by date, not by label. That is the practical lesson, and it is why the rest of this piece talks only about dates.
Why "upgrade to the latest" costs you time
Here is the trap, stated as plainly as the dates allow. Day counts are as of this update, 22 October 2026; the end-of-life dates are fixed.
| Version | Released | End of life | Days left at this update | Risk score |
|---|---|---|---|---|
| 12.0 (newest) | 2026-10-16 | 2027-01-15 | 85 | 25 |
| 11.11 | 2026-09-16 | 2026-12-15 | 54 | 25 |
| 11.10 | 2026-08-14 | 2026-11-15 | 24 | 25 |
| 11.9 | 2026-07-16 | 2026-10-15 | past | 35 |
| 11.8 | 2026-06-16 | 2026-09-15 | past | 35 |
| 11.7 | 2026-05-15 | 2027-05-15 | 205 | 10 |
| 10.11 (yours, probably) | 2025-08-15 | 2026-08-15 | past | 35 |
11.7 is older than 12.0 and outlives it by 120 days. Upgrading to the newest release buys you three months and then puts you back in the same position, having spent the same testing and rollout effort you would have spent going to 11.7.
The 11.10 release is the point restated. It shipped on August 14, 2026, one day before 10.11 died, so it is the obvious destination for anyone reacting to that deadline — and it expires on November 15, 2026, six months before the release that came out three months ahead of it. The 11.11 release of September 16, 2026 repeats the pattern: three months of support, to December 15, 2026. So does the 12.0 major release of October 16, 2026, supported to January 15, 2027.
Anyone following the ordinary rule — take the latest stable — ends up doing this migration twice. Nothing in the version numbers signals which release has the long runway.
What is still supported
Four versions as of 22 October 2026, and that is the complete list:
| Version | Supported until | Verdict |
|---|---|---|
| 11.7 | 2027-05-15 | The target. Nearly seven months of runway. |
| 12.0 | 2027-01-15 | Newest, but expires January 15, 2027. |
| 11.11 | 2026-12-15 | Expires December 15, 2026. |
| 11.10 | 2026-11-15 | Expires November 15, 2026. |
Everything else in the Mattermost catalogue — all 54 other tracked releases — is already past end of life. Current patch levels for each supported line are on the Mattermost lifecycle page, which is rebuilt from upstream data rather than typed here.
What to do
If you are on 10.11: plan the move to 11.7, not to 12.0. You are jumping a major version either way, so the testing burden is the same; the difference is whether the result lasts nearly seven months or three.
If you are on 11.8: it reached end of life on September 15, 2026, so you are in the same position as 10.11 users, and the same target applies.
If you upgraded to 11.9: it ended on October 15, 2026, so you are already unsupported; move to 11.7 rather than chasing the newest release. If you upgraded to 11.10, 11.11 or 12.0: you are supported, but 11.10 ends November 15, 2026, 11.11 ends December 15, 2026 and 12.0 ends January 15, 2027. Put the next migration in the calendar now rather than meeting it by surprise, and consider whether moving sideways to 11.7 is cheaper than two upgrades.
If you have not moved off 10.11 yet: the realistic controls are the ordinary ones for an unpatched internal service — restrict network exposure, make sure it is not reachable from the public internet, and write the decision down with a date attached. Undocumented end-of-life software is what auditors record as a finding.
Every Mattermost version, its dates and its EOL Risk Score are on the Mattermost lifecycle page, updated at every build from upstream data.
Frequently Asked Questions
When did Mattermost 11.9 reach end of life?
Mattermost 11.9's end of life date is October 15, 2026, so it is no longer supported. It was released on July 16, 2026 with the standard three-month window that most Mattermost feature releases receive. On that date its security fixes stopped, and the best target for the move off it is 11.7, which is supported until May 15, 2027, not the newest release.
Which Mattermost versions are still supported today?
As of October 22, 2026, four lines are supported: 11.7 until May 15, 2027, 11.10 until November 15, 2026, 11.11 until December 15, 2026 and 12.0 until January 15, 2027. Mattermost 11.9 ended on October 15, 2026, Mattermost 11.8 ended on September 15, 2026 and 10.11 ended on August 15, 2026. Every other tracked release is already past end of life.
How long is a Mattermost release supported?
Mattermost ships a new server version on the 16th of each month, and a feature release is supported for about three months, roughly one release of overlap. Across the 58 releases we track, 45 got three months, and only two, 10.11 and 11.7, got twelve. The newest release, 12.0, shipped on October 16, 2026 and is supported until January 15, 2027.
What does the Extended Support Release (ESR/LTS) label mean for Mattermost?
Mattermost's release policy describes an Extended Support Release as a release maintained for a longer period that receives backports for security fixes and major bug fixes, with ESRs released every nine months and supported for twelve. Mattermost's release page marks 10.11 and 11.7 as ESRs: 10.11 ran from August 15, 2025 to August 15, 2026, and 11.7 runs from May 15, 2026 to May 15, 2027. The LTS flag in the lifecycle data we carry sits on seven older releases, the most recent of them 10.5, which ended on November 15, 2025, so pick a target by its end-of-life date rather than by any label.
What should a team on an ended Mattermost version do?
Plan the move to 11.7, which is supported until May 15, 2027, rather than to the newest release, which expires first. If you are still on 10.11, which ended on August 15, 2026, or 11.8, which ended on September 15, 2026, the testing burden of the jump is the same either way; the difference is how long the result lasts. There is no third-party extended-support market for Mattermost that we know of, so until the upgrade lands, restrict the server's network exposure and record the decision with a date.