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Fencer Vulns
critical 9.8

CVE-2026-64523 in the critical feed json

net/handshake: Take a long-lived file reference at submit

published 2026-07-25 3 mo ago modified 2026-11-03 5 d ago also EUVD-2026-48867

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 39%
public exploits
0
none known

Summary

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

net/handshake: Take a long-lived file reference at submit

handshake_nl_accept_doit() needs the file pointer backing req->hr_sk->sk_socket to survive the window between handshake_req_next() and the subsequent FD_PREPARE() and get_file(). The submit-side sock_hold() does not provide that. sk_refcnt keeps struct sock alive, but struct socket is owned by sock->file: when the consumer fputs the last file reference, sock_release() tears the socket down regardless of any sock_hold.

Add an hr_file pointer to struct handshake_req and acquire an explicit reference on sock->file during handshake_req_submit(). handshake_complete() and handshake_req_cancel() release the reference on the completion-bit-winning path.

The submit error path must also release the file reference, but after rhashtable insertion a concurrent handshake_req_cancel() can discover the request and race the error path. Gate the error-path cleanup -- sk_destruct restoration, fput, and request destruction -- with test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED), the same serialization handshake_complete() and handshake_req_cancel() already use. When cancel has already claimed ownership, the submit error path returns without touching the request; socket teardown handles final destruction.

The accept-side dereferences are not yet retargeted; that change comes in the next patch.

Patch / fix

  • Linux Linux 6.6.160, 6.12.93, 6.18.44, 7.0.12, 7.1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-64523

  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1008.8
  • linux-gke Ubuntu 26.04 LTS 7.0.0-1003.4
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1010.10
  • linux-azure Ubuntu 26.04 LTS 7.0.0-1010.10
  • linux-raspi Ubuntu 26.04 LTS 7.0.0-1015.15
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-28.28.1

ubuntu advisories UBUNTU-CVE-2026-64523

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 AlmaLinux 10 6.12.0-211.69.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.69.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.69.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.69.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.69.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.69.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.69.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.69.1.el10_2

almalinux advisories ALSA-2026:91565ALSA-2026:90365

  • kernel Rocky Linux 9 5.14.0-687.61.1.el9_8.cloud.1.0
  • kernel Rocky Linux 10 6.12.0-211.69.1.el10_2
  • kernel Rocky Linux 9 5.14.0-687.61.1.el9_8

rocky linux advisories RXSA-2026:90365RLSA-2026:91565RLSA-2026:90365

  • kernel Azure Linux 3.0 6.6.161.1-1

azure linux advisories AZL-93725

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-64523 updated cvss 7.0

kernel: net/handshake: Take a long-lived file reference at submit

  • 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
    affected: no fix available
  • Red Hat Enterprise Linux kernel-modules-internal 6.12.0-211.69.1.el10_2
    fixed: vendor fix RHSA-2026:91565
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.61.1.el9_8, perf 5.14.0-687.61.1.el9_8, rtla 5.14.0-687.61.1.el9_8, python3-perf 5.14.0-687.61.1.el9_8, kernel-devel-matched 5.14.0-687.61.1.el9_8, kernel-64k-devel-matched 5.14.0-687.61.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:90365
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.69.1.el10_2, perf 6.12.0-211.69.1.el10_2, rtla 6.12.0-211.69.1.el10_2, python3-perf 6.12.0-211.69.1.el10_2, kernel-devel-matched 6.12.0-211.69.1.el10_2, kernel-64k-devel-matched 6.12.0-211.69.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:91565
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.61.1.el9_8, kernel-64k 5.14.0-687.61.1.el9_8, kernel-core 5.14.0-687.61.1.el9_8, kernel-tools 5.14.0-687.61.1.el9_8, kernel-modules 5.14.0-687.61.1.el9_8, kernel-64k-core 5.14.0-687.61.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:90365
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.69.1.el10_2, kernel-64k 6.12.0-211.69.1.el10_2, kernel-core 6.12.0-211.69.1.el10_2, kernel-tools 6.12.0-211.69.1.el10_2, kernel-modules 6.12.0-211.69.1.el10_2, kernel-64k-core 6.12.0-211.69.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:91565
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.61.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.61.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.61.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.61.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.61.1.el9_8
    fixed: vendor fix RHSA-2026:90365
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.69.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.69.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.69.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.69.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.69.1.el10_2 Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal 6.12.0-211.69.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.69.1.el10_2
    fixed: vendor fix RHSA-2026:91565
show 5 more
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.61.1.el9_8, kernel-rt-64k 5.14.0-687.61.1.el9_8, kernel-rt-core 5.14.0-687.61.1.el9_8, kernel-rt-modules 5.14.0-687.61.1.el9_8, kernel-rt-64k-core 5.14.0-687.61.1.el9_8, kernel-rt-debug-core 5.14.0-687.61.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:90365
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.69.1.el10_2, kernel-rt-64k 6.12.0-211.69.1.el10_2, kernel-rt-core 6.12.0-211.69.1.el10_2, kernel-rt-modules 6.12.0-211.69.1.el10_2, kernel-rt-64k-core 6.12.0-211.69.1.el10_2, kernel-rt-debug-core 6.12.0-211.69.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:91565
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.61.1.el9_8, kernel-rt-core 5.14.0-687.61.1.el9_8, kernel-rt-modules 5.14.0-687.61.1.el9_8, kernel-rt-debug-core 5.14.0-687.61.1.el9_8, kernel-rt-modules-core 5.14.0-687.61.1.el9_8, kernel-rt-debug-modules 5.14.0-687.61.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:90365
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.69.1.el10_2, kernel-rt-core 6.12.0-211.69.1.el10_2, kernel-rt-modules 6.12.0-211.69.1.el10_2, kernel-rt-debug-core 6.12.0-211.69.1.el10_2, kernel-rt-modules-core 6.12.0-211.69.1.el10_2, kernel-rt-debug-modules 6.12.0-211.69.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:91565
  • 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
    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

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
23 d ago

Exploit prediction

0.45% chance of exploitation in the next 30 days, higher than 39% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
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.