After a year of working on the bug, Firefox now runs stably on PCs with Intel Raptor Lake processors.

Mozilla fixed crashes in Firefox caused by Intel Raptor Lake processors

The Mozilla company has finished work on a critical bug that caused the Firefox browser to crash on desktop computers with Intel Raptor Lake (13th and 14th generation) chips. Normal operation was restored in Firefox 151.01; the fix took more than a year.

What happened
- The error occurred during the `zlib-rs` compression routine.
- Incorrectly calculated `dist` values caused out-of-bounds array access, leading to browser crashes.
- The root cause lay in Raptor Lake processor instructions (RPL050 and RPL060), which sometimes returned incorrect or stale data.

How it was discovered
Senior developer Gabriele Svelto noticed the issue last year, blaming Intel for unstable chip performance. He filed numerous complaints about Firefox crashes, especially in hot regions. After updating Intel microcode to 0x12c, crash frequency dropped, but when version 0x12F was released, errors returned.

Why processors became a problem
Since late 2022, widespread issues with Raptor Lake emerged. The manufacturer confirmed that the cause was physical degradation of chips due to prolonged high voltage and heat. Microcode helped mitigate crashes but did not fully restore processor functionality. In response, Intel extended warranty from 3 to 5 years.

What users should do
If you have a laptop or PC based on Intel Raptor Lake (13th and 14th generation), be sure to update Firefox to the latest version (151.01+). This will eliminate crashes and ensure stable browser operation.