CVE-2026-52973
Received Received - Intake
futex Hash Allocation Fix in Linux Kernel

Publication date: 2026-06-24

Last updated on: 2026-06-24

Assigner: kernel.org

Description
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.
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Meta Information
Published
2026-06-24
Last Modified
2026-06-24
Generated
2026-06-25
AI Q&A
2026-06-24
EPSS Evaluated
N/A
NVD
CVE-2026-52973
EUVD
EUVD-2026-38841
Affected Vendors & Products
Currently, no data is known.
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Exploitability
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KEV
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CWE ID Description
CWE-UNKNOWN
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Executive Summary

This vulnerability exists in the Linux kernel's futex subsystem. It arises because the function need_futex_hash_allocate_default() relies on strict pthread semantics by requiring the CLONE_THREAD flag. This assumption breaks when the memory descriptor (mm) is shared in other ways, causing concurrency issues.

Specifically, this leads to a bug such as a slab-use-after-free error detected by KASAN (Kernel Address Sanitizer) in futex_hash_put, where a per-CPU counter can be incorrectly referenced after it has been freed.

The fix loosens the requirement from CLONE_THREAD to any CLONE_VM clone except vfork(), which prevents races and maintains performance on existing paths.

Impact Analysis

This vulnerability can cause kernel bugs such as use-after-free errors, which may lead to system instability or crashes.

Because it involves concurrency and memory management in the kernel, exploitation could potentially lead to denial of service or unpredictable behavior in applications relying on futexes.

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