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critical 9.8

CVE-2026-63979 in the critical feed json

net/handshake: hand off the pinned file reference to accept_doit

published 3mo ago modified 21d ago also EUVD-2026-45752

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

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

net/handshake: hand off the pinned file reference to accept_doit

handshake_req_next() removes the request from the per-net pending list and drops hn_lock before handshake_nl_accept_doit() reads req->hr_sk->sk_socket and dereferences sock->file (once in FD_PREPARE() and again in get_file()). In that window a consumer running tls_handshake_cancel() followed by sockfd_put() (svc_sock_free) or __fput_sync() (xs_reset_transport) releases sock->file. sock_release() then runs sock_orphan(), zeroing sk_socket, and frees the struct socket. The accept-side code either reads NULL through sk_socket or chases freed memory.

The submit-side sock_hold() does not prevent this. sk_refcnt protects struct sock, but struct socket and sock->file are independently refcounted via the file descriptor the consumer owns. Pinning sk leaves sock and sock->file unprotected.

Retarget the accept-side dereferences at req->hr_file, which was pinned at submit time, instead of req->hr_sk->sk_socket->file. Pinning on its own is not sufficient: a consumer that cancels between handshake_req_next() returning and accept_doit reaching FD_PREPARE() takes the !remove_pending() branch in handshake_req_cancel() and drops hr_file before the accept side takes its own reference. Hand off an additional file reference inside handshake_req_next(), under hn_lock, so the accept side operates on a reference that no concurrent handshake_req_cancel() can revoke. FD_PREPARE() consumes that handed-off reference, either by transferring it to the new fd in fd_publish() or by dropping it in the cleanup destructor on error; the explicit get_file() that previously balanced FD_PREPARE() is therefore redundant and goes away.

Update handshake_req_cancel_test2 and _test3 to simulate the FD_PREPARE() consumption with an fput() so the kunit file-count assertions stay balanced.

Patch / fix

  • Linux Linux 6.6.160, 6.12.114, 6.18.44, 7.0.12, 7.1
  • linux Debian 13 6.12.115-2
  • linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-63979

  • 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-2026-63979

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

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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-2026-63979 updated cvss 8.1

kernel: net/handshake: hand off the pinned file reference to accept_doit

  • 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
  • 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
show 4 more
  • 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 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
    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
26d ago

Exploit prediction

0.64% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-11).

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 Intel 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.