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Fencer Vulns
high 7.8

CVE-2023-53781 json

smc: Fix use-after-free in tcp_write_timer_handler().

published 2025-12-09 11 mo ago modified 2026-10-30 10 d ago also EUVD-2023-60125

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 4%
public exploits
0
none known

Summary

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

smc: Fix use-after-free in tcp_write_timer_handler().

With Eric's ref tracker, syzbot finally found a repro for use-after-free in tcp_write_timer_handler() by kernel TCP sockets. [0]

If SMC creates a kernel socket in __smc_create(), the kernel socket is supposed to be freed in smc_clcsock_release() by calling sock_release() when we close() the parent SMC socket.

However, at the end of smc_clcsock_release(), the kernel socket's sk_state might not be TCP_CLOSE. This means that we have not called inet_csk_destroy_sock() in __tcp_close() and have not stopped the TCP timers.

The kernel socket's TCP timers can be fired later, so we need to hold a refcnt for net as we do for MPTCP subflows in mptcp_subflow_create_socket().

[0]: leaked reference. sk_alloc (./include/net/net_namespace.h:335 net/core/sock.c:2108) inet_create (net/ipv4/af_inet.c:319 net/ipv4/af_inet.c:244) __sock_create (net/socket.c:1546) smc_create (net/smc/af_smc.c:3269 net/smc/af_smc.c:3284) __sock_create (net/socket.c:1546) __sys_socket (net/socket.c:1634 net/socket.c:1618 net/socket.c:1661) __x64_sys_socket (net/socket.c:1672) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) ================================================================== BUG: KASAN: slab-use-after-free in tcp_write_timer_handler (net/ipv4/tcp_timer.c:378 net/ipv4/tcp_timer.c:624 net/ipv4/tcp_timer.c:594) Read of size 1 at addr ffff888052b65e0d by task syzrepro/18091

CPU: 0 PID: 18091 Comm: syzrepro Tainted: G W 6.3.0-rc4-01174-gb5d54eb5899a #7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.amzn2022.0.1 04/01/2014 Call Trace: <IRQ> dump_stack_lvl (lib/dump_stack.c:107) print_report (mm/kasan/report.c:320 mm/kasan/report.c:430) kasan_report (mm/kasan/report.c:538) tcp_write_timer_handler (net/ipv4/tcp_timer.c:378 net/ipv4/tcp_timer.c:624 net/ipv4/tcp_timer.c:594) tcp_write_timer (./include/linux/spinlock.h:390 net/ipv4/tcp_timer.c:643) call_timer_fn (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/timer.h:127 kernel/time/timer.c:1701) __run_timers.part.0 (kernel/time/timer.c:1752 kernel/time/timer.c:2022) run_timer_softirq (kernel/time/timer.c:2037) __do_softirq (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/irq.h:142 kernel/softirq.c:572) __irq_exit_rcu (kernel/softirq.c:445 kernel/softirq.c:650) irq_exit_rcu (kernel/softirq.c:664) sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1107 (discriminator 14)) </IRQ>

Patch / fix

  • Linux Linux 6.1.191, 6.2.12, 6.3
  • linux Debian 14, Debian 13 6.3.7-1

debian advisories DEBIAN-CVE-2023-53781

  • kernel RHEL 8 4.18.0-553.132.1.el8_10
  • perf RHEL 8 4.18.0-553.132.1.el8_10
  • bpftool RHEL 8 4.18.0-553.132.1.el8_10
  • kernel-core RHEL 8 4.18.0-553.132.1.el8_10
  • kernel-tools RHEL 8 4.18.0-553.132.1.el8_10
  • python3-perf RHEL 8 4.18.0-553.132.1.el8_10
  • kernel-modules RHEL 8 4.18.0-553.132.1.el8_10
  • kernel-zfcpdump RHEL 8 4.18.0-553.132.1.el8_10

red hat advisories RHSA-2026:77301RHSA-2026:69906RHSA-2026:69874RHSA-2026:25121RHSA-2026:25120RHSA-2025:20518

  • kernel-64kb SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS, SLE High Performance Computing 15 SP4-ESPOS 5.14.21-150400.24.194.1
  • kernel-syms SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +1 more 5.14.21-150400.24.194.1
  • kernel-source SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +1 more 5.14.21-150400.24.194.1
  • kernel-default SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE Micro 5.4 +5 more 5.14.21-150400.24.194.1
  • kernel-obs-build SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +1 more 5.14.21-150400.24.194.1
  • kernel-default-base SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE Micro 5.4 +3 more 5.14.21-150400.24.194.1.150400.24.98.3
  • kernel-rt SLE Micro 5.4, SLE Micro 5.3 5.14.21-150400.15.142.1
  • kernel-source-rt SLE Micro 5.4, SLE Micro 5.3 5.14.21-150400.15.142.1

suse advisories SUSE-SU-2026:1088-1SUSE-SU-2026:1048-1SUSE-SU-2026:1049-1SUSE-SU-2026:1046-1SUSE-SU-2026:1044-1SUSE-SU-2026:1039-1

  • kernel-rt AlmaLinux 8 4.18.0-553.132.1.rt7.473.el8_10
  • kernel-rt-core AlmaLinux 8 4.18.0-553.132.1.rt7.473.el8_10
  • kernel-rt-modules AlmaLinux 8 4.18.0-553.132.1.rt7.473.el8_10
  • kernel-rt-debug-core AlmaLinux 8 4.18.0-553.132.1.rt7.473.el8_10
  • kernel-rt-debug-modules AlmaLinux 8 4.18.0-553.132.1.rt7.473.el8_10
  • kernel-rt-modules-extra AlmaLinux 8 4.18.0-553.132.1.rt7.473.el8_10
  • kernel-rt-debug-modules-extra AlmaLinux 8 4.18.0-553.132.1.rt7.473.el8_10
  • kernel AlmaLinux 8 4.18.0-553.132.1.el8_10

almalinux advisories ALSA-2026:25120ALSA-2026:25121

  • kernel Rocky Linux 8 4.18.0-553.132.1.el8_10.cloud.0.1
  • kernel-rt Rocky Linux 8 4.18.0-553.132.1.rt7.473.el8_10
  • kernel Rocky Linux 8 4.18.0-553.132.1.el8_10

rocky linux advisories RXSA-2026:25121RLSA-2026:25120RLSA-2026:25121

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-2023-53781 updated cvss 7.3

kernel: smc: Fix use-after-free in tcp_write_timer_handler()

  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-611.5.1.el9_7, perf 5.14.0-611.5.1.el9_7, rtla 5.14.0-611.5.1.el9_7, python3-perf 5.14.0-611.5.1.el9_7, kernel-devel-matched 5.14.0-611.5.1.el9_7, kernel-64k-devel-matched 5.14.0-611.5.1.el9_7, +7 more
    fixed: vendor fix RHSA-2025:20518
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.132.1.el8_10, kernel 4.18.0-553.132.1.el8_10, bpftool 4.18.0-553.132.1.el8_10, kernel-core 4.18.0-553.132.1.el8_10, kernel-tools 4.18.0-553.132.1.el8_10, python3-perf 4.18.0-553.132.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:25121
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-611.5.1.el9_7, kernel-64k 5.14.0-611.5.1.el9_7, kernel-core 5.14.0-611.5.1.el9_7, kernel-tools 5.14.0-611.5.1.el9_7, kernel-modules 5.14.0-611.5.1.el9_7, kernel-64k-core 5.14.0-611.5.1.el9_7, +27 more
    fixed: vendor fix RHSA-2025:20518
  • Red Hat Enterprise Linux BaseOS AUS (v.8.4) perf 4.18.0-305.208.1.el8_4, kernel 4.18.0-305.208.1.el8_4, bpftool 4.18.0-305.208.1.el8_4, kernel-core 4.18.0-305.208.1.el8_4, kernel-tools 4.18.0-305.208.1.el8_4, python3-perf 4.18.0-305.208.1.el8_4, +8 more
    fixed: vendor fix RHSA-2026:69874
  • Red Hat Enterprise Linux BaseOS AUS (v.8.6) perf 4.18.0-372.216.1.el8_6, kernel 4.18.0-372.216.1.el8_6, bpftool 4.18.0-372.216.1.el8_6, kernel-core 4.18.0-372.216.1.el8_6, kernel-tools 4.18.0-372.216.1.el8_6, python3-perf 4.18.0-372.216.1.el8_6, +8 more
    fixed: vendor fix RHSA-2026:69906
  • Red Hat Enterprise Linux BaseOS E4S (v.8.8) perf 4.18.0-477.172.1.el8_8, kernel 4.18.0-477.172.1.el8_8, bpftool 4.18.0-477.172.1.el8_8, kernel-core 4.18.0-477.172.1.el8_8, kernel-tools 4.18.0-477.172.1.el8_8, python3-perf 4.18.0-477.172.1.el8_8, +9 more
    fixed: vendor fix RHSA-2026:77301
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) perf 4.18.0-305.208.1.el8_4, kernel 4.18.0-305.208.1.el8_4, bpftool 4.18.0-305.208.1.el8_4, kernel-core 4.18.0-305.208.1.el8_4, kernel-tools 4.18.0-305.208.1.el8_4, python3-perf 4.18.0-305.208.1.el8_4, +15 more
    fixed: vendor fix RHSA-2026:69874
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6) perf 4.18.0-372.216.1.el8_6, kernel 4.18.0-372.216.1.el8_6, bpftool 4.18.0-372.216.1.el8_6, kernel-core 4.18.0-372.216.1.el8_6, kernel-tools 4.18.0-372.216.1.el8_6, python3-perf 4.18.0-372.216.1.el8_6, +15 more
    fixed: vendor fix RHSA-2026:69906
show 7 more
  • Red Hat Enterprise Linux BaseOS TUS (v.8.8) perf 4.18.0-477.172.1.el8_8, kernel 4.18.0-477.172.1.el8_8, bpftool 4.18.0-477.172.1.el8_8, kernel-core 4.18.0-477.172.1.el8_8, kernel-tools 4.18.0-477.172.1.el8_8, python3-perf 4.18.0-477.172.1.el8_8, +8 more
    fixed: vendor fix RHSA-2026:77301
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-611.5.1.el9_7, kernel-debuginfo-common-s390x 5.14.0-611.5.1.el9_7, kernel-debuginfo-common-x86_64 5.14.0-611.5.1.el9_7, kernel-debuginfo-common-aarch64 5.14.0-611.5.1.el9_7, kernel-debuginfo-common-ppc64le 5.14.0-611.5.1.el9_7
    fixed: vendor fix RHSA-2025:20518
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.132.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.132.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.132.1.el8_10
    fixed: vendor fix RHSA-2026:25121
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.132.1.rt7.473.el8_10, kernel-rt-kvm 4.18.0-553.132.1.rt7.473.el8_10, kernel-rt-core 4.18.0-553.132.1.rt7.473.el8_10, kernel-rt-modules 4.18.0-553.132.1.rt7.473.el8_10, kernel-rt-debug-kvm 4.18.0-553.132.1.rt7.473.el8_10, kernel-rt-debug-core 4.18.0-553.132.1.rt7.473.el8_10, +4 more
    fixed: vendor fix RHSA-2026:25120
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-611.5.1.el9_7, kernel-rt-64k 5.14.0-611.5.1.el9_7, kernel-rt-core 5.14.0-611.5.1.el9_7, kernel-rt-modules 5.14.0-611.5.1.el9_7, kernel-rt-64k-core 5.14.0-611.5.1.el9_7, kernel-rt-debug-core 5.14.0-611.5.1.el9_7, +14 more Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-611.5.1.el9_7, kernel-rt-core 5.14.0-611.5.1.el9_7, kernel-rt-modules 5.14.0-611.5.1.el9_7, kernel-rt-debug-core 5.14.0-611.5.1.el9_7, kernel-rt-modules-core 5.14.0-611.5.1.el9_7, kernel-rt-debug-modules 5.14.0-611.5.1.el9_7, +4 more
    fixed: vendor fix RHSA-2025:20518
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.132.1.rt7.473.el8_10, kernel-rt-core 4.18.0-553.132.1.rt7.473.el8_10, kernel-rt-modules 4.18.0-553.132.1.rt7.473.el8_10, kernel-rt-debug-core 4.18.0-553.132.1.rt7.473.el8_10, kernel-rt-debug-modules 4.18.0-553.132.1.rt7.473.el8_10, kernel-rt-modules-extra 4.18.0-553.132.1.rt7.473.el8_10, +2 more
    fixed: vendor fix RHSA-2026:25120
  • 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 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
    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
no
Technical impact
total
Assessed
24 d ago

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% 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

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.