Linux Kernel kthread startup delay fixes SMP boot hang
CVE-2026-99250 Published on November 3, 2026
printk: Postpone kthread startup
In the Linux kernel, the following vulnerability has been resolved:
printk: Postpone kthread startup
There have been various bug reports related to SMP systems hanging
on boot. The reports vary but seem to have some overlap with regard
to missed IPI's during SMP setup. The reports also show that
reverting NBCON console usage allows the bugs to disappear.
The NBCON kthreads for console printing are started very early
during boot using early_initcall(). Since these kthreads are
asynchronously enabling/disabling interrupts during early boot, they
may be interfering with early SMP setup on some hardware platforms.
Starting the console printing kthreads later has shown to avoid the
hanging on systems that could previously reproduce the issue.
Postpone kthread starting until after all arch initcalls have
completed.
Products Associated with CVE-2026-99250
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Affected Versions
Linux:- Version 76f258bf3f2aae570209319944703a92ac64e29e and below a86bcdd84c8fe7a45f73e12d53fe06fea07d1ceb is affected.
- Version 76f258bf3f2aae570209319944703a92ac64e29e and below 7595bacee48bc30b5021eccf199d704d4e5e5374 is affected.
- Version 76f258bf3f2aae570209319944703a92ac64e29e and below 792acd173da0884f0172c68cb473f42cf93c647e is affected.
- Version 76f258bf3f2aae570209319944703a92ac64e29e and below 5f339c46f153184570f16c8e789c9709b14cbe8b is affected.
- Version 6.12 is affected.
- Before 6.12 is unaffected.
- Version 6.12.115, <= 6.12.* is unaffected.
- Version 6.18.59, <= 6.18.* is unaffected.
- Version 7.2.13, <= 7.2.* is unaffected.
- Version 7.3, <= * is unaffected.