CVE-2026-64229 x86/mm: Disable broadcast TLB flush when PCID is disabled
A local attacker can cause a kernel crash by triggering a general protection fault when booting with the nopcid option on AMD CPUs.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64229?
CVE-2026-64229 is a medium-severity vulnerability in Linux kernel, published on 24 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
x86/mm: Disable broadcast TLB flush when PCID is disabled
Booting with "nopcid" clears X86_FEATURE_PCID and keeps CR4.PCIDE from being set to one. On AMD CPUs that support INVLPGB, broadcast TLB flushing remains enabled.
There are two checks that decide whether the global ASID code runs, mm_global_asid() and consider_global_asid(), that key off of the X86_FEATURE_INVLPGB feature. Once an mm becomes active on more than three CPUs, consider_global_asid() assigns it a global ASID, after which flush_tlb_mm_range() takes the broadcast_tlb_flush() path using a non-zero PCID. Issuing an INVLPGB with a non-zero PCID while CR4.PCIDE is not set results in a #GP:
Oops: general protection fault, kernel NULL pointer dereference 0x1: 0000 [#1] SMP NOPTI CPU: 158 UID: 0 PID: 3119 Comm: snap Not tainted 7.1.0-rc3 #1 PREEMPT(full) Hardware name: ... RIP: 0010:broadcast_tlb_flush Code: ... 89 da 48 83 c8 07 <0f> 01 fe eb 08 cc cc cc ... Call Trace: <TASK> flush_tlb_mm_range ptep_clear_flush wp_page_copy ? _raw_spin_unlock __handle_mm_fault handle_mm_fault do_user_addr_fault exc_page_fault asm_exc_page_fault
All processors that support broadcast TLB invalidation also have PCID support, so it is only the "nopcid" scenario that is of concern. In this situation just disable the broadcast TLB support using the CPUID dependency support by making X86_FEATURE_INVLPGB dependent on X86_FEATURE_PCID.
[ bp: Massage commit message. ]
Weakness: CWE-476
Which versions are affected by CVE-2026-64229?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64229?
Apply the vendor's patch.
Is CVE-2026-64229 being exploited?
There is no known exploitation of CVE-2026-64229 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64229, DEBIAN-CVE-2026-64229, GHSA-qc88-p59g-xj3v, ROOT-OS-UBUNTU-2204-CVE-2026-64229, UBUNTU-CVE-2026-64229.