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CVE-2026-80775— futex: Fix race on the initial mm->futex.phash.ref allocation

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于futex_hash_allocate()在分配mm->futex.phash.ref时未加锁，存在竞争条件，可能导致释放后使用，从而使任务在futex_q_lock()中写入已释放内存。

AI Predicted 5.5 Difficulty: Hard EPSS 0.17% · P6

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux d9b05321e21e4b218de4ce8a590bf375f58b6346< 86d12b34bafc9a4c271a9edefea88855a934d6e5 affected
d9b05321e21e4b218de4ce8a590bf375f58b6346< ff252ed45c8263525f2f54d81c5fa6d547fba344 affected
d9b05321e21e4b218de4ce8a590bf375f58b6346< c4b4972d8edcdf50b6518f55119e129d2f668a10 affected
d9b05321e21e4b218de4ce8a590bf375f58b6346< bde0238083647381d4747355c5a19115a3422b96 affected
6.17 affected
< 6.17 unaffected
6.18.47≤ 6.18.* unaffected
7.1.11≤ 7.1.* unaffected
… +2 more rows
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I. Basic Information for CVE-2026-80775

Vulnerability Information
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Vulnerability Title
futex: Fix race on the initial mm->futex.phash.ref allocation
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: futex: Fix race on the initial mm->futex.phash.ref allocation futex_hash_allocate() allocates mm->futex.phash.ref without any locking. Commit d9b05321e21e ("futex: Move futex_hash_free() back to __mmput()") moved the allocation here and assumed that the process has just a single thread at this point. Commit ee9dce44362b ("futex: Drop CLONE_THREAD requirement for private default hash alloc") widened need_futex_hash_allocate_default() to cover any CLONE_VM clone, but left out vfork because the parent is suspended and cannot race. That no longer holds once vfork is nested. If a vfork child calls vfork again and is then killed with SIGKILL, the parent is released from its vfork wait and runs concurrently with the grandchild in the same mm. Neither of them went through futex_hash_allocate_default(). When both call prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS) at the same time, each one sees mm->futex.phash.ref as NULL and stores its own percpu counter. Only the last store survives. The counter stored first is no longer reachable from the mm, so the references on it are not seen by __futex_ref_atomic_end(). A private hash that still has references is then considered dead and freed, and a task that still holds one of its buckets writes into freed memory in futex_q_lock(). Store the counter once with cmpxchg() and let the loser free_percpu() its own. The initial reference has to be taken before the store, otherwise another task can install a private hash while the counter is still 0.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于futex_hash_allocate()在分配mm->futex.phash.ref时未加锁，存在竞争条件，可能导致释放后使用，从而使任务在futex_q_lock()中写入已释放内存。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux d9b05321e21e4b218de4ce8a590bf375f58b6346 ~ 86d12b34bafc9a4c271a9edefea88855a934d6e5 -
Linux Linux 6.17 -

II. Public POCs for CVE-2026-80775

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III. Intelligence Information for CVE-2026-80775

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Patches & Fixes for CVE-2026-80775 (4)

Same Patch Batch · Linux · 2026-09-04 · 156 CVEs total

CVE-2026-80865 bpf: Add missing access_ok call to copy_user_syms
CVE-2026-80856 fuse: fix invalidate lock leak on setattr writeback failure
CVE-2026-80857 fuse: wait for FR_FINISHED on abort_on_kill to prevent use-after-free
CVE-2026-80858 fuse: publish io-uring queues with release semantics
CVE-2026-80859 fuse: fix missing barrier when checking io-uring readiness
CVE-2026-80860 fuse: fix race between interrupt and resend
CVE-2026-80861 usb: xhci: bail out of setup if the controller is inaccessible
CVE-2026-80862 nvme-tcp: fix usage of page_frag_cache
CVE-2026-80863 RDMA/rxe: Fix OOB in free_rd_atomic_resources()
CVE-2026-80864 RDMA/rxe: Fix responder UAF on IB_QP_MAX_DEST_RD_ATOMIC modify_qp
CVE-2026-80870 drm/amdkfd: Validate CRIU-restored IDs before idr_alloc
CVE-2026-80874 arm64: dts: renesas: ironhide: Describe inline ECC carveouts
CVE-2026-80873 KVM: arm64: nv: Write ESR_EL2 for injected nested SError exceptions
CVE-2026-80872 ALSA: hda/tas2781: Cancel async firmware request at unbind
CVE-2026-80871 crypto: xilinx-trng - Remove crypto_rng interface
CVE-2026-80868 ntfs3: Allocate iomap inline_data using alloc_page
CVE-2026-80866 tipc: avoid busy looping in tipc_exit_net()
CVE-2026-80867 alpha/PCI: Add security_locked_down() check to pci_mmap_resource()
CVE-2026-80855 fuse: fix invalidate lock leak on open O_TRUNC DAX failure
CVE-2026-80869 ntfs: bound the attribute-list entry in ntfs_read_inode_mount()

Showing top 20 of 156 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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