CVE-2026-52973

Summary

In the Linux kernel, the following vulnerability has been resolved:

futex: Drop CLONE_THREAD requirement for private default hash alloc

Currently need_futex_hash_allocate_default() depends on strict pthread semantics, abusing CLONE_THREAD. This breaks the non-concurrency assumptions when doing the mm->futex_ref pcpu allocations, leading to bugs[0] when sharing the mm in other ways; ie:

BUG: KASAN: slab-use-after-free in futex_hash_put

… where the +1 bias can end up on a percpu counter that mm->futex_ref no longer points at.

Loosen the check to cover any CLONE_VM clone, except vfork(). Excluding vfork keeps the existing paths untouched (no overhead), and we can't race in the first place: either the parent is suspended and the child runs alone, or mm->futex_ref is already allocated from an earlier CLONE_VM.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxd9b05321e21e4b218de4ce8a590bf375f58b6346 < 1dcd36420af2da5bd59306dba9caf78e3d248b1daffected
LinuxLinuxd9b05321e21e4b218de4ce8a590bf375f58b6346 < 974ac49a9a068b0591a59f65c63eb06579a13091affected
LinuxLinuxd9b05321e21e4b218de4ce8a590bf375f58b6346 < ee9dce44362b2d8132c32964656ab6dff7dfbc6aaffected
LinuxLinux6.17affected
LinuxLinux0 < 6.17unaffected
LinuxLinux6.18.33 <= 6.18.*unaffected
LinuxLinux7.0.10 <= 7.0.*unaffected
LinuxLinux7.1 <= *unaffected

Weaknesses

ADP Enrichment

kernel: futex: Drop CLONE_THREAD requirement for private default hash alloc

Additional References

References