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Fencer Vulns
critical 9.8

CVE-2026-23240 in the critical feed json

tls: Fix race condition in tls_sw_cancel_work_tx()

published 2026-03-10 8 mo ago modified 2026-10-19 20 d ago also EUVD-2026-10575

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:

tls: Fix race condition in tls_sw_cancel_work_tx()

This issue was discovered during a code audit.

After cancel_delayed_work_sync() is called from tls_sk_proto_close(), tx_work_handler() can still be scheduled from paths such as the Delayed ACK handler or ksoftirqd. As a result, the tx_work_handler() worker may dereference a freed TLS object.

The following is a simple race scenario:

cpu0 cpu1

tls_sk_proto_close() tls_sw_cancel_work_tx() tls_write_space() tls_sw_write_space() if (!test_and_set_bit(BIT_TX_SCHEDULED, &tx_ctx->tx_bitmask)) set_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask); cancel_delayed_work_sync(&ctx->tx_work.work); schedule_delayed_work(&tx_ctx->tx_work.work, 0);

To prevent this race condition, cancel_delayed_work_sync() is replaced with disable_delayed_work_sync().

Patch / fix

  • Linux Linux 6.12.75, 6.18.16, 6.19.6, 7.0
  • linux Debian 13 6.12.85-1
  • linux Debian 14 6.19.6-1

debian advisories DEBIAN-CVE-2026-23240

  • linux-nvidia-tegra Ubuntu 24.04 LTS 6.8.0-1035.38

ubuntu advisories UBUNTU-CVE-2026-23240

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-livepatch-MICRO-6-0_Update_21 Linux Micro 6.1, Linux Micro 6.0 5-1.1
  • kernel-livepatch-MICRO-6-0_Update_22 Linux Micro 6.1, Linux Micro 6.0 5-1.1
  • kernel-livepatch-MICRO-6-0-RT_Update_14 Linux Micro 6.1, Linux Micro 6.0 11-1.1
  • kernel-livepatch-MICRO-6-0-RT_Update_10 Linux Micro 6.1, Linux Micro 6.0 20-1.1
  • kernel-livepatch-MICRO-6-0-RT_Update_11 Linux Micro 6.1, Linux Micro 6.0 16-1.1
  • kernel-livepatch-MICRO-6-0-RT_Update_12 Linux Micro 6.1, Linux Micro 6.0 15-1.1
  • kernel-livepatch-MICRO-6-0-RT_Update_13 Linux Micro 6.1, Linux Micro 6.0 11-1.1
  • kernel-livepatch-MICRO-6-0-RT_Update_15 Linux Micro 6.1, Linux Micro 6.0 10-1.1

suse advisories SUSE-SU-2026:23483-1SUSE-SU-2026:23484-1SUSE-SU-2026:23531-1SUSE-SU-2026:23532-1SUSE-SU-2026:23482-1SUSE-SU-2026:23541-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.28.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.28.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.28.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.28.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.28.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.28.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.28.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.28.1

opensuse advisories openSUSE-SU-2026:20572-1openSUSE-SU-2026:10387-1

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-2026-23240 updated cvss 5.8

kernel: Linux kernel: Denial of service due to a race condition in the TLS subsystem

  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 10 kernel
    affected: no fix available
  • 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 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
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
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.