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Fencer Vulns
high 7.8

CVE-2026-52947 json

net: qrtr: fix refcount saturation and potential UAF in qrtr_port_remove

published 2026-06-24 4 mo ago modified 2026-10-19 20 d ago also EUVD-2026-38815

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits
0
none known

Summary

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

net: qrtr: fix refcount saturation and potential UAF in qrtr_port_remove

In qrtr_port_remove(), the socket reference count is decremented via __sock_put() before the port is removed from the qrtr_ports XArray and before the RCU grace period elapses.

This breaks the fundamental RCU update paradigm. It exposes a race window where a concurrent RCU reader (such as qrtr_reset_ports() or qrtr_port_lookup()) can obtain a pointer to the socket from the XArray, and attempt to call sock_hold() on a socket whose reference count has already dropped to zero.

This exact race condition was hit during syzkaller fuzzing, leading to the following refcount saturation warning and a potential Use-After-Free:

refcount_t: saturated; leaking memory. WARNING: CPU: 3 PID: 1273 at lib/refcount.c:22 refcount_warn_saturate+0xae/0x1d0 Modules linked in: qrtr(+) bochs drm_shmem_helper ... Call Trace: <TASK> qrtr_reset_ports net/qrtr/af_qrtr.c:768 [inline] [qrtr] __qrtr_bind.isra.0+0x48b/0x570 net/qrtr/af_qrtr.c:805 [qrtr] qrtr_bind+0x17d/0x210 net/qrtr/af_qrtr.c:901 [qrtr] kernel_bind+0xe4/0x120 net/socket.c:3592 qrtr_ns_init+0x1a6/0x380 net/qrtr/ns.c:715 [qrtr] qrtr_proto_init+0x3b/0xff0 net/qrtr/af_qrtr.c:169 [qrtr] do_one_initcall+0xf5/0x5e0 init/main.c:1283 ... </TASK>

Fix this by deferring the reference count decrement until after the xa_erase() and the synchronize_rcu() complete.

(Note: The v1 of this patch incorrectly replaced __sock_put() with sock_put(). As Simon Horman pointed out, the callers of qrtr_port_remove() still hold a reference to the socket, so freeing the socket memory here would lead to a subsequent UAF in the caller. Thus, the __sock_put() is kept, but only repositioned to close the RCU race.)

Patch / fix

  • Linux Linux 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, 7.0.13, 7.1
  • linux Debian 12 6.1.176-1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.13-1

debian advisories DEBIAN-CVE-2026-52947

  • linux Ubuntu 22.04 LTS 5.15.0-198.208
  • linux Ubuntu 24.04 LTS 6.8.0-146.146
  • linux Ubuntu 26.04 LTS 7.0.0-31.31
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1117.124
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1066.69
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1012.12
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1118.128
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1070.78

ubuntu advisories UBUNTU-CVE-2026-52947

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-rt RHEL 8 4.18.0-553.163.1.rt7.504.el8_10
  • kernel-rt-kvm RHEL 8 4.18.0-553.163.1.rt7.504.el8_10
  • kernel-rt-core RHEL 8 4.18.0-553.163.1.rt7.504.el8_10
  • kernel-rt-modules RHEL 8 4.18.0-553.163.1.rt7.504.el8_10
  • kernel-rt-debug-kvm RHEL 8 4.18.0-553.163.1.rt7.504.el8_10
  • kernel-rt-debug-core RHEL 8 4.18.0-553.163.1.rt7.504.el8_10
  • kernel-rt-debug-modules RHEL 8 4.18.0-553.163.1.rt7.504.el8_10
  • kernel-rt-modules-extra RHEL 8 4.18.0-553.163.1.rt7.504.el8_10

red hat advisories RHSA-2026:67469RHSA-2026:67468RHSA-2026:67150RHSA-2026:65334

  • kernel-rt Real Time Module 15 SP7 6.4.0-150700.7.72.1
  • kernel-syms-rt Real Time Module 15 SP7 6.4.0-150700.7.72.1
  • kernel-source-rt Real Time Module 15 SP7 6.4.0-150700.7.72.1
  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.78.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.78.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.78.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.78.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.78.1

suse advisories SUSE-SU-2026:3810-1SUSE-SU-2026:3790-1SUSE-SU-2026:23244-1SUSE-SU-2026:23241-1SUSE-SU-2026:23194-1SUSE-SU-2026:23193-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.37.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.37.1

opensuse advisories openSUSE-SU-2026:21555-1

  • kernel AlmaLinux 8 4.18.0-553.163.1.el8_10
  • perf AlmaLinux 8 4.18.0-553.163.1.el8_10
  • bpftool AlmaLinux 8 4.18.0-553.163.1.el8_10
  • kernel-core AlmaLinux 8 4.18.0-553.163.1.el8_10
  • kernel-tools AlmaLinux 8 4.18.0-553.163.1.el8_10
  • python3-perf AlmaLinux 8 4.18.0-553.163.1.el8_10
  • kernel-modules AlmaLinux 8 4.18.0-553.163.1.el8_10
  • kernel-zfcpdump AlmaLinux 8 4.18.0-553.163.1.el8_10

almalinux advisories ALSA-2026:67468ALSA-2026:67469ALSA-2026:67150ALSA-2026:65334

  • kernel-rt Rocky Linux 8 4.18.0-553.163.1.rt7.504.el8_10
  • kernel Rocky Linux 8 4.18.0-553.163.1.el8_10
  • kernel Rocky Linux 9 5.14.0-687.47.1.el9_8
  • kernel Rocky Linux 10 6.12.0-211.53.1.el10_2

rocky linux advisories RLSA-2026:67469RLSA-2026:67468RLSA-2026:67150RLSA-2026:65334

  • kernel Azure Linux 3.0 6.6.143.1-1

azure linux advisories AZL-90486

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-2026-52947 updated cvss 4.7

kernel: net: qrtr: fix refcount saturation and potential UAF in qrtr_port_remove

  • 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: workaround, no fix available
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.47.1.el9_8, perf 5.14.0-687.47.1.el9_8, rtla 5.14.0-687.47.1.el9_8, python3-perf 5.14.0-687.47.1.el9_8, kernel-devel-matched 5.14.0-687.47.1.el9_8, kernel-64k-devel-matched 5.14.0-687.47.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:67150
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.53.1.el10_2, perf 6.12.0-211.53.1.el10_2, rtla 6.12.0-211.53.1.el10_2, python3-perf 6.12.0-211.53.1.el10_2, kernel-devel-matched 6.12.0-211.53.1.el10_2, kernel-64k-devel-matched 6.12.0-211.53.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:65334
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.163.1.el8_10, kernel 4.18.0-553.163.1.el8_10, bpftool 4.18.0-553.163.1.el8_10, kernel-core 4.18.0-553.163.1.el8_10, kernel-tools 4.18.0-553.163.1.el8_10, python3-perf 4.18.0-553.163.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:67468
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.47.1.el9_8, kernel-64k 5.14.0-687.47.1.el9_8, kernel-core 5.14.0-687.47.1.el9_8, kernel-tools 5.14.0-687.47.1.el9_8, kernel-modules 5.14.0-687.47.1.el9_8, kernel-64k-core 5.14.0-687.47.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:67150
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.53.1.el10_2, kernel-64k 6.12.0-211.53.1.el10_2, kernel-core 6.12.0-211.53.1.el10_2, kernel-tools 6.12.0-211.53.1.el10_2, kernel-modules 6.12.0-211.53.1.el10_2, kernel-64k-core 6.12.0-211.53.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:65334
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.47.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.47.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.47.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.47.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.47.1.el9_8
    fixed: vendor fix RHSA-2026:67150
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.53.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.53.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.53.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.53.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.53.1.el10_2
    fixed: vendor fix RHSA-2026:65334
show 8 more
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.163.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.163.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.163.1.el8_10
    fixed: vendor fix RHSA-2026:67468
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.163.1.rt7.504.el8_10, kernel-rt-kvm 4.18.0-553.163.1.rt7.504.el8_10, kernel-rt-core 4.18.0-553.163.1.rt7.504.el8_10, kernel-rt-modules 4.18.0-553.163.1.rt7.504.el8_10, kernel-rt-debug-kvm 4.18.0-553.163.1.rt7.504.el8_10, kernel-rt-debug-core 4.18.0-553.163.1.rt7.504.el8_10, +4 more
    fixed: vendor fix RHSA-2026:67469
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.47.1.el9_8, kernel-rt-64k 5.14.0-687.47.1.el9_8, kernel-rt-core 5.14.0-687.47.1.el9_8, kernel-rt-modules 5.14.0-687.47.1.el9_8, kernel-rt-64k-core 5.14.0-687.47.1.el9_8, kernel-rt-debug-core 5.14.0-687.47.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:67150
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.53.1.el10_2, kernel-rt-64k 6.12.0-211.53.1.el10_2, kernel-rt-core 6.12.0-211.53.1.el10_2, kernel-rt-modules 6.12.0-211.53.1.el10_2, kernel-rt-64k-core 6.12.0-211.53.1.el10_2, kernel-rt-debug-core 6.12.0-211.53.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:65334
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.47.1.el9_8, kernel-rt-core 5.14.0-687.47.1.el9_8, kernel-rt-modules 5.14.0-687.47.1.el9_8, kernel-rt-debug-core 5.14.0-687.47.1.el9_8, kernel-rt-modules-core 5.14.0-687.47.1.el9_8, kernel-rt-debug-modules 5.14.0-687.47.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:67150
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.53.1.el10_2, kernel-rt-core 6.12.0-211.53.1.el10_2, kernel-rt-modules 6.12.0-211.53.1.el10_2, kernel-rt-debug-core 6.12.0-211.53.1.el10_2, kernel-rt-modules-core 6.12.0-211.53.1.el10_2, kernel-rt-debug-modules 6.12.0-211.53.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:65334
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.163.1.rt7.504.el8_10, kernel-rt-core 4.18.0-553.163.1.rt7.504.el8_10, kernel-rt-modules 4.18.0-553.163.1.rt7.504.el8_10, kernel-rt-debug-core 4.18.0-553.163.1.rt7.504.el8_10, kernel-rt-debug-modules 4.18.0-553.163.1.rt7.504.el8_10, kernel-rt-modules-extra 4.18.0-553.163.1.rt7.504.el8_10, +2 more
    fixed: vendor fix RHSA-2026:67469
  • 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
    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 ICSA-26-295-16 updated cvss 7.8

Siemens SIMATIC S7-1500 TM MFP

  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
24 d ago

Exploit prediction

0.11% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux
  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
  • CWE-416 Use After Free
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.