Linux Kernel KVM: Slab UAF on Vendor Module Reload
CVE-2026-68428 Published on August 10, 2026
KVM: x86/mmu: Fix use-after-free on vendor module reload
In the Linux kernel, the following vulnerability has been resolved:
KVM: x86/mmu: Fix use-after-free on vendor module reload
mmu_destroy_caches() destroys pte_list_desc_cache and
mmu_page_header_cache, but leaves both pointers unchanged. The pointers
live in kvm.ko, and therefore survive when a vendor module is unloaded
while kvm.ko remains loaded.
If creation of pte_list_desc_cache fails during a subsequent vendor
module load, its assignment sets pte_list_desc_cache to NULL and the
error path calls mmu_destroy_caches(). mmu_page_header_cache still
points to the cache destroyed during the preceding vendor module
unload. Passing that stale pointer to kmem_cache_destroy() causes a
slab use-after-free.
Reproduce the issue on a v7.1.3 kernel with CONFIG_KASAN=y,
CONFIG_KASAN_GENERIC=y, CONFIG_KVM=m, and CONFIG_KVM_INTEL=m. A
one-shot test hook forces pte_list_desc_cache to NULL on the second
invocation of kvm_mmu_vendor_module_init():
1. Load kvm.ko and kvm-intel.ko, creating both caches.
2. Unload only kvm_intel, leaving kvm.ko loaded.
3. Reload kvm_intel and force initialization through the -ENOMEM path.
KASAN reports:
BUG: KASAN: slab-use-after-free in
kvm_mmu_vendor_module_init+0x5b/0x170 [kvm]
...
kmem_cache_destroy+0x21/0x1d0
kvm_mmu_vendor_module_init+0x5b/0x170 [kvm]
...
Allocated by task 16817:
__kmem_cache_create_args+0x12c/0x3b0
__kmem_cache_create.constprop.0+0xb6/0xf0 [kvm]
kvm_mmu_vendor_module_init+0x13b/0x170 [kvm]
...
Freed by task 16820:
kmem_cache_destroy+0x117/0x1d0
kvm_mmu_vendor_module_exit+0x21/0x30 [kvm]
Clear both pointers immediately after destroying their caches so that
the stored state reflects the caches' lifetime and repeated cleanup is
safe.
With the fix applied, the same injected vendor module reload fails with
-ENOMEM as expected and produces no KASAN report.
Products Associated with CVE-2026-68428
Want to know whenever a new CVE is published for Linux Kernel? stack.watch will email you.
Affected Versions
Linux:- Version cb498ea2ce1d3f3c0bc0a2522241dca10263e437 and below 6f4be73880302d5642c83a0813fdfe1f5fd4b6e3 is affected.
- Version cb498ea2ce1d3f3c0bc0a2522241dca10263e437 and below 32b9f89ed9e6d7a45075d64089c254a7f6e13695 is affected.
- Version cb498ea2ce1d3f3c0bc0a2522241dca10263e437 and below ec9daa8fd1b6f45545c9839dca55bd867fad9e13 is affected.
- Version cb498ea2ce1d3f3c0bc0a2522241dca10263e437 and below 43cfb20d62ffe49626d62beecfc32eb6f262191c is affected.
- Version cb498ea2ce1d3f3c0bc0a2522241dca10263e437 and below 52f2f7c30126037975389aa04d24c506a5177c35 is affected.
- Version 2.6.25 is affected.
- Before 2.6.25 is unaffected.
- Version 6.6.148, <= 6.6.* is unaffected.
- Version 6.12.101, <= 6.12.* is unaffected.
- Version 6.18.42, <= 6.18.* is unaffected.
- Version 7.1.6, <= 7.1.* is unaffected.
- Version 7.2-rc5, <= * is unaffected.