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Fencer Vulns
critical 9.8

CVE-2026-64541 in the critical feed json

net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket

published 2026-07-27 3 mo ago modified 2026-11-03 5 d ago also EUVD-2026-49592

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 47%
public exploits
0
none known

Summary

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

net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket

smc_cdc_rx_handler() looks up the connection by token under the link group's conns_lock, drops the lock, and then dereferences conn and the smc_sock derived from it, ending in sock_hold(&smc->sk) inside smc_cdc_msg_recv(). No reference is held across the lock release.

The only reference pinning the socket while the connection is discoverable in the link group is taken in smc_lgr_register_conn() (sock_hold) and dropped in __smc_lgr_unregister_conn() (sock_put), both under conns_lock. Once the handler drops conns_lock, a concurrent close() -> smc_release() -> smc_conn_free() -> smc_lgr_unregister_conn() can drop that reference and free the smc_sock, so the handler's later sock_hold() runs on freed memory:

WARNING: lib/refcount.c:25 at refcount_warn_saturate Workqueue: rxe_wq do_work refcount_warn_saturate (lib/refcount.c:25) smc_cdc_msg_recv (net/smc/smc_cdc.c:430) smc_cdc_rx_handler (net/smc/smc_cdc.c:502) smc_wr_rx_tasklet_fn (net/smc/smc_wr.c:445) tasklet_action_common (kernel/softirq.c:938) handle_softirqs (kernel/softirq.c:622) Kernel panic - not syncing: panic_on_warn set

Only SMC-R is affected. The SMC-D receive tasklet is stopped by tasklet_kill(&conn->rx_tsklet) in smc_conn_free() before the connection is unregistered, so it cannot run concurrently with the free.

Take the socket reference while still holding conns_lock, so the registration reference can no longer be the last one, and drop it once the handler is done.

Patch / fix

  • Linux Linux 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5, 7.2
  • linux Debian 12 6.1.180-1
  • linux Debian 13 6.12.100-1
  • linux Debian 14 7.1.5-1
  • linux-6.12 Debian 12 6.12.100-1~deb12u1

debian advisories DEBIAN-CVE-2026-64541

  • linux Ubuntu 22.04 LTS 5.15.0-198.208
  • linux Ubuntu 24.04 LTS 6.8.0-147.147
  • linux Ubuntu 26.04 LTS 7.0.0-34.34
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1117.124
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1067.70
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1013.13
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1118.128
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1071.79

ubuntu advisories UBUNTU-CVE-2026-64541

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-64kb SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS, SLE High Performance Computing 15 SP5-ESPOS 5.14.21-150500.55.189.1
  • kernel-syms SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS +1 more 5.14.21-150500.55.189.1
  • kernel-source SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +2 more 5.14.21-150500.55.189.1
  • kernel-default SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +3 more 5.14.21-150500.55.189.1
  • kernel-obs-build SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS +1 more 5.14.21-150500.55.189.1
  • kernel-default-base SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +2 more 5.14.21-150500.55.189.1.150500.6.87.4
  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1

suse advisories SUSE-SU-2026:4595-1SUSE-SU-2026:4254-1SUSE-SU-2026:4369-1SUSE-SU-2026:4347-1SUSE-SU-2026:4284-1SUSE-SU-2026:23887-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.38.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.38.1

opensuse advisories openSUSE-SU-2026:21910-1openSUSE-SU-2026:11476-1

  • kernel AlmaLinux 9 5.14.0-687.66.1.el9_8
  • rv AlmaLinux 9 5.14.0-687.66.1.el9_8
  • perf AlmaLinux 9 5.14.0-687.66.1.el9_8
  • rtla AlmaLinux 9 5.14.0-687.66.1.el9_8
  • libperf AlmaLinux 9 5.14.0-687.66.1.el9_8
  • kernel-rt AlmaLinux 9 5.14.0-687.66.1.el9_8
  • kernel-64k AlmaLinux 9 5.14.0-687.66.1.el9_8
  • kernel-core AlmaLinux 9 5.14.0-687.66.1.el9_8

almalinux advisories ALSA-2026:95370ALSA-2026:95100ALSA-2026:95212

  • kernel Rocky Linux 9 5.14.0-687.66.1.el9_8
  • kernel-rt Rocky Linux 8 4.18.0-553.184.1.rt7.525.el8_10
  • kernel Rocky Linux 8 4.18.0-553.184.1.el8_10

rocky linux advisories RLSA-2026:95370RLSA-2026:95100RLSA-2026:95212

  • kernel Azure Linux 3.0 6.6.145.2-1

azure linux advisories AZL-94026

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-2026-64541 updated cvss 5.9

kernel: net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket

  • 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 Enterprise Linux 10 kernel 6.12.0-250.el10
    affected: workaround, no fix available
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.66.1.el9_8, perf 5.14.0-687.66.1.el9_8, rtla 5.14.0-687.66.1.el9_8, python3-perf 5.14.0-687.66.1.el9_8, kernel-devel-matched 5.14.0-687.66.1.el9_8, kernel-64k-devel-matched 5.14.0-687.66.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:95370
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.184.1.el8_10, kernel 4.18.0-553.184.1.el8_10, bpftool 4.18.0-553.184.1.el8_10, kernel-core 4.18.0-553.184.1.el8_10, kernel-tools 4.18.0-553.184.1.el8_10, python3-perf 4.18.0-553.184.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:95212
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.66.1.el9_8, kernel-64k 5.14.0-687.66.1.el9_8, kernel-core 5.14.0-687.66.1.el9_8, kernel-tools 5.14.0-687.66.1.el9_8, kernel-modules 5.14.0-687.66.1.el9_8, kernel-64k-core 5.14.0-687.66.1.el9_8, +27 more Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.66.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.66.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.66.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.66.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.66.1.el9_8
    fixed: vendor fix RHSA-2026:95370
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.184.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.184.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.184.1.el8_10
    fixed: vendor fix RHSA-2026:95212
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.184.1.rt7.525.el8_10, kernel-rt-kvm 4.18.0-553.184.1.rt7.525.el8_10, kernel-rt-core 4.18.0-553.184.1.rt7.525.el8_10, kernel-rt-modules 4.18.0-553.184.1.rt7.525.el8_10, kernel-rt-debug-kvm 4.18.0-553.184.1.rt7.525.el8_10, kernel-rt-debug-core 4.18.0-553.184.1.rt7.525.el8_10, +4 more
    fixed: vendor fix RHSA-2026:95100
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.66.1.el9_8, kernel-rt-64k 5.14.0-687.66.1.el9_8, kernel-rt-core 5.14.0-687.66.1.el9_8, kernel-rt-modules 5.14.0-687.66.1.el9_8, kernel-rt-64k-core 5.14.0-687.66.1.el9_8, kernel-rt-debug-core 5.14.0-687.66.1.el9_8, +14 more Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.66.1.el9_8, kernel-rt-core 5.14.0-687.66.1.el9_8, kernel-rt-modules 5.14.0-687.66.1.el9_8, kernel-rt-debug-core 5.14.0-687.66.1.el9_8, kernel-rt-modules-core 5.14.0-687.66.1.el9_8, kernel-rt-debug-modules 5.14.0-687.66.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:95370
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.184.1.rt7.525.el8_10, kernel-rt-core 4.18.0-553.184.1.rt7.525.el8_10, kernel-rt-modules 4.18.0-553.184.1.rt7.525.el8_10, kernel-rt-debug-core 4.18.0-553.184.1.rt7.525.el8_10, kernel-rt-debug-modules 4.18.0-553.184.1.rt7.525.el8_10, kernel-rt-modules-extra 4.18.0-553.184.1.rt7.525.el8_10, +2 more
    fixed: vendor fix RHSA-2026:95100
show 1 more
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +2 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +9 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

0.56% chance of exploitation in the next 30 days, higher than 47% 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.