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, 11.11, expires on December 15, 2026, while a version released four months earlier runs until May 15, 2027. Getting this backwards means doing the upgrade work twice before Christmas.
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 57 releases tracked as of this update:
| Support window | Releases | What it means |
|---|---|---|
| 3 months | 44 | The standard. Roughly one release of overlap. 11.11 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-seven. 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: both 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 does mark certain releases as long-term-support, and our lifecycle data carries that flag. Seven releases have it: 10.5, 9.11, 8.1, 7.8, 7.5, 7.1 and 6.3.
Neither 10.11 nor 11.7 is among them — and every one of those seven is already end-of-life, the most recent having expired in November 2025.
| Group | Releases | Typical window | Status today |
|---|---|---|---|
| Flagged long-term-support | 7 | ~9 months | All 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. If you pick your target version by looking for the long-term-support marker, you will land on something that expired months ago rather than on 11.7.
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, 17 September 2026; the end-of-life dates are fixed.
| Version | Released | End of life | Days left at this update | Risk score |
|---|---|---|---|---|
| 11.11 (newest) | 2026-09-16 | 2026-12-15 | 89 | 25 |
| 11.10 | 2026-08-14 | 2026-11-15 | 59 | 25 |
| 11.9 | 2026-07-16 | 2026-10-15 | 28 | 25 |
| 11.8 | 2026-06-16 | 2026-09-15 | past | 35 |
| 11.7 | 2026-05-15 | 2027-05-15 | 240 | 10 |
| 10.11 (yours, probably) | 2025-08-15 | 2026-08-15 | past | 35 |
11.7 is older than 11.11 and outlives it by 151 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.
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 17 September 2026, and that is the complete list:
| Version | Supported until | Verdict |
|---|---|---|
| 11.7 | 2027-05-15 | The target. Eight months of runway. |
| 11.11 | 2026-12-15 | Newest, but expires December 15, 2026. |
| 11.10 | 2026-11-15 | Expires November 15, 2026. |
| 11.9 | 2026-10-15 | Expires October 15, 2026. Not a destination. |
Everything else in the Mattermost catalogue — all 53 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 11.11. You are jumping a major version either way, so the testing burden is the same; the difference is whether the result lasts eight 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 already upgraded to 11.9, 11.10 or 11.11: you are supported, but 11.9 ends October 15, 2026, 11.10 ends November 15, 2026 and 11.11 ends December 15, 2026. 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.