Skip to content
Fencer Vulns
no cvss —

CVE-2026-80775 json

futex: Fix race on the initial mm->futex.phash.ref allocation

published 2026-09-04 2 mo ago modified 2026-10-19 21 d ago also EUVD-2026-71418

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 8%
public exploits
0
none known

Summary

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.

Patch / fix

  • Linux Linux 6.18.47, 7.1.11, 7.2.1, 7.3
  • linux Debian 14 7.1.12-1

debian advisories DEBIAN-CVE-2026-80775

  • linux Ubuntu 26.04 LTS 7.0.0-42.42
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1016.17
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1016.18
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1017.17
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-42.42.1
  • linux-oracle Ubuntu 26.04 LTS 7.0.0-1015.16
  • linux-hwe-7.0 Ubuntu 24.04 LTS 7.0.0-42.42~24.04.1
  • linux-oem-7.0 Ubuntu 26.04 LTS 7.0.0-1017.17

ubuntu advisories UBUNTU-CVE-2026-80775

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 9 5.14.0-687.54.1.el9_8
  • rv RHEL 9 5.14.0-687.54.1.el9_8
  • perf RHEL 9 5.14.0-687.54.1.el9_8
  • rtla RHEL 9 5.14.0-687.54.1.el9_8
  • libperf RHEL 9 5.14.0-687.54.1.el9_8
  • kernel-rt RHEL 9 5.14.0-687.54.1.el9_8
  • kernel-64k RHEL 9 5.14.0-687.54.1.el9_8
  • kernel-core RHEL 9 5.14.0-687.54.1.el9_8

red hat advisories RHSA-2026:74438

  • kernel-source openSUSE Tumbleweed 7.2.5-1.1

opensuse advisories openSUSE-SU-2026:11773-1

  • kernel AlmaLinux 10 6.12.0-211.63.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.63.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.63.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.63.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.63.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.63.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.63.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.63.1.el10_2

almalinux advisories ALSA-2026:76738ALSA-2026:74438

  • kernel Rocky Linux 9 5.14.0-687.54.1.el9_8

rocky linux advisories RLSA-2026:74438

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-80775 updated cvss 7.0

kernel: futex: Fix race on the initial mm->futex.phash.ref allocation

  • Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available
  • Red Hat Enterprise Linux kernel-modules-internal 6.12.0-211.63.1.el10_2
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.54.1.el9_8, perf 5.14.0-687.54.1.el9_8, rtla 5.14.0-687.54.1.el9_8, python3-perf 5.14.0-687.54.1.el9_8, kernel-devel-matched 5.14.0-687.54.1.el9_8, kernel-64k-devel-matched 5.14.0-687.54.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:74438
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.63.1.el10_2, perf 6.12.0-211.63.1.el10_2, rtla 6.12.0-211.63.1.el10_2, python3-perf 6.12.0-211.63.1.el10_2, kernel-devel-matched 6.12.0-211.63.1.el10_2, kernel-64k-devel-matched 6.12.0-211.63.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.54.1.el9_8, kernel-64k 5.14.0-687.54.1.el9_8, kernel-core 5.14.0-687.54.1.el9_8, kernel-tools 5.14.0-687.54.1.el9_8, kernel-modules 5.14.0-687.54.1.el9_8, kernel-64k-core 5.14.0-687.54.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:74438
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.63.1.el10_2, kernel-64k 6.12.0-211.63.1.el10_2, kernel-core 6.12.0-211.63.1.el10_2, kernel-tools 6.12.0-211.63.1.el10_2, kernel-modules 6.12.0-211.63.1.el10_2, kernel-64k-core 6.12.0-211.63.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.54.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.54.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.54.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.54.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.54.1.el9_8
    fixed: vendor fix RHSA-2026:74438
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.63.1.el10_2 Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.63.1.el10_2
    fixed: vendor fix RHSA-2026:76738
show 6 more
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.54.1.el9_8, kernel-rt-64k 5.14.0-687.54.1.el9_8, kernel-rt-core 5.14.0-687.54.1.el9_8, kernel-rt-modules 5.14.0-687.54.1.el9_8, kernel-rt-64k-core 5.14.0-687.54.1.el9_8, kernel-rt-debug-core 5.14.0-687.54.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:74438
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.63.1.el10_2, kernel-rt-64k 6.12.0-211.63.1.el10_2, kernel-rt-core 6.12.0-211.63.1.el10_2, kernel-rt-modules 6.12.0-211.63.1.el10_2, kernel-rt-64k-core 6.12.0-211.63.1.el10_2, kernel-rt-debug-core 6.12.0-211.63.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.54.1.el9_8, kernel-rt-core 5.14.0-687.54.1.el9_8, kernel-rt-modules 5.14.0-687.54.1.el9_8, kernel-rt-debug-core 5.14.0-687.54.1.el9_8, kernel-rt-modules-core 5.14.0-687.54.1.el9_8, kernel-rt-debug-modules 5.14.0-687.54.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:74438
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.63.1.el10_2, kernel-rt-core 6.12.0-211.63.1.el10_2, kernel-rt-modules 6.12.0-211.63.1.el10_2, kernel-rt-debug-core 6.12.0-211.63.1.el10_2, kernel-rt-modules-core 6.12.0-211.63.1.el10_2, kernel-rt-debug-modules 6.12.0-211.63.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat OpenShift Container Platform 4.22 rhcos 4.22.9.8.202610061719
    fixed: vendor fix RHSA-2026:79151
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.18% chance of exploitation in the next 30 days, higher than 8% of all scored CVEs (FIRST EPSS, 2026-11-08).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.