CVE-2026-80775futex: Fix race on the initial mm->futex.phash.ref allocation
- —Not scoredno CVSS score yet
- 0.18%Exploitation in 30 daysEPSS · top 92% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By Linux
- 9 days later
· 9 days later
Published
- 45 days later
· 45 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.
- EPSS (exploitation in 30 days)
- 0.18% · top 92% of all CVEs (15 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.
Affected products
- affected d9b05321e21e4b218de4ce8a590bf375f58b6346 – < 86d12b34bafc9a4c271a9edefea88855a934d6e5
- affected d9b05321e21e4b218de4ce8a590bf375f58b6346 – < ff252ed45c8263525f2f54d81c5fa6d547fba344
- affected d9b05321e21e4b218de4ce8a590bf375f58b6346 – < c4b4972d8edcdf50b6518f55119e129d2f668a10
- affected d9b05321e21e4b218de4ce8a590bf375f58b6346 – < bde0238083647381d4747355c5a19115a3422b96
- affected 6.17
- unaffected < 6.17
- unaffected 6.18.47 – ≤ 6.18.*
- unaffected 7.1.11 – ≤ 7.1.*
- unaffected 7.2.1 – ≤ 7.2.*
- unaffected 7.3 – ≤ *
References
References4
- https://git.kernel.org/stable/c/86d12b34bafc9a4c271a9edefea88855a934d6e5 (opens in a new tab)
- https://git.kernel.org/stable/c/ff252ed45c8263525f2f54d81c5fa6d547fba344 (opens in a new tab)
- https://git.kernel.org/stable/c/c4b4972d8edcdf50b6518f55119e129d2f668a10 (opens in a new tab)
- https://git.kernel.org/stable/c/bde0238083647381d4747355c5a19115a3422b96 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-71418 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-80775)Record last updated .