Should you update to Thunderbird 152?
No: install Thunderbird 159 instead. Thunderbird 152 is a security update Mozilla released on 16 Jun 2026 for Mac, Windows and Linux. It fixes 40 security flaws, 0 rated critical and 13 high by Mozilla.[1] None of them is known to be used in attacks.
It has since been replaced by Thunderbird 152.0.1, released 30 Jun 2026, which includes all of its fixes. If you’re on an older version, install that instead.
Should you update?
No: install Thunderbird 159 instead. Thunderbird 159 came out on 27 Oct 2026 and includes every fix in Thunderbird 152, so there’s no reason to stop at this one. Software Update offers the newest version your device can run.
Is Thunderbird 152 still safe?
Not any more. The 9 updates since, up to Thunderbird 159, fix 560 security flaws that Thunderbird 152 doesn’t, and each became public the day its fix shipped. Installing it is safe: get it only from Thunderbird’s own About window, or thunderbird.net, never from a link in an email, text or pop-up.
What it fixes
Mozilla lists 40 security flaws, 0 rated critical and 13 high by Mozilla.[1] The 13 critical and high ones are:
| Flaw | Severity | What Mozilla calls it |
|---|---|---|
CVE-2026-12289 | High | Privilege escalation in the Graphics: WebRender component |
CVE-2026-12290 | High | Memory safety bug fixed in Thunderbird 152 |
CVE-2026-12291 | High | Use-after-free in the Networking: HTTP component |
CVE-2026-12292 | High | Incorrect boundary conditions in the Web Audio component |
CVE-2026-12293 | High | Use-after-free in the Graphics: WebGPU component |
CVE-2026-12294 | High | Sandbox escape in the DOM: Workers component |
CVE-2026-12295 | High | Sandbox escape in the DOM: Navigation component |
CVE-2026-12296 | High | Sandbox escape in the Security: Process Sandboxing component |
CVE-2026-12297 | High | Sandbox escape due to incorrect boundary conditions in the Networking component |
CVE-2026-12298 | High | Memory safety bug fixed in Thunderbird 152 |
CVE-2026-12299 | High | JIT miscompilation in the DOM: Core & HTML component |
CVE-2026-12326 | High | Memory safety bugs fixed in Firefox 152 and Thunderbird 152 |
CVE-2026-12328 | High | Memory safety bugs fixed in Firefox ESR 115.37, Firefox ESR 140.12, Thunderbird ESR 140.12, Firefox 152 and Thunderbird 152 |
How to update, and how long it takes
A minute or two. Thunderbird restarts and your mail stays where it was.
- Open Thunderbird.On a Mac choose Thunderbird → About Thunderbird; on Windows open the ☰ menu → Help → About Thunderbird.
- Let it download the update.The About window checks for one by itself; when it says “Restart to update Thunderbird”, click it.
To check it worked: The same About Thunderbird window shows the version under the name. It should say 152.0.1 or later.
Before and after
- After: Thunderbird 152.0.1, 30 Jun 2026, 2 security flaws
- Thunderbird updates, every release and the latest version
- Updates, the latest version of everything HARD tracks
References
- ^ Mozilla. “Mozilla Foundation Security Advisory MFSA 2026-60”, 16 Jun 2026.