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Fencer Intel
high 8.4

CVE-2026-63952 json

memfd: deny writeable mappings when implying SEAL_WRITE

published 3mo ago modified 14d ago also EUVD-2026-45725

cvss
8.4
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 2%
public exploits
0
none known

Summary

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

memfd: deny writeable mappings when implying SEAL_WRITE

When SEAL_EXEC is added, SEAL_WRITE is implied to make W^X. But the implied seal is set after the check that makes sure the memfd can not have any writable mappings. This means one can use SEAL_EXEC to apply SEAL_WRITE while having writeable mappings.

This breaks the contract that SEAL_WRITE provides and can be used by an attacker to pass a memfd that appears to be write sealed but can still be modified arbitrarily.

Fix this by adding the implied seals before the call for mapping_deny_writable() is done.

Patch / fix

  • Linux Linux 6.6.143, 6.12.93, 6.18.35, 7.0.12, 7.1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-63952

  • linux Ubuntu 24.04 LTS 6.8.0-146.146
  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1066.69
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1070.78
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1008.8
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1065.73
  • linux-gke Ubuntu 26.04 LTS 7.0.0-1003.4

ubuntu advisories UBUNTU-CVE-2026-63952

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 RHEL 9 5.14.0-687.41.1.el9_8
  • rv RHEL 9 5.14.0-687.41.1.el9_8
  • perf RHEL 9 5.14.0-687.41.1.el9_8
  • rtla RHEL 9 5.14.0-687.41.1.el9_8
  • libperf RHEL 9 5.14.0-687.41.1.el9_8
  • kernel-rt RHEL 9 5.14.0-687.41.1.el9_8
  • kernel-64k RHEL 9 5.14.0-687.41.1.el9_8
  • kernel-core RHEL 9 5.14.0-687.41.1.el9_8

red hat advisories RHSA-2026:69089RHSA-2026:67720RHSA-2026:57252RHSA-2026:57251

  • kernel-default SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Live Patching 15 SP6 +1 more 6.4.0-150600.23.130.1
  • 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

suse advisories SUSE-SU-2026:3602-1SUSE-SU-2026:3810-1SUSE-SU-2026:3790-1SUSE-SU-2026:23244-1SUSE-SU-2026:23241-1SUSE-SU-2026:23194-1

  • 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 10 6.12.0-211.49.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.49.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.49.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.49.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.49.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.49.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.49.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.49.1.el10_2

almalinux advisories ALSA-2026:57251ALSA-2026:57252

  • kernel Rocky Linux 10 6.12.0-211.49.1.el10_2
  • kernel Rocky Linux 9 5.14.0-687.41.1.el9_8

rocky linux advisories RLSA-2026:57251RLSA-2026:57252

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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-2026-63952 updated cvss 7.0

kernel: memfd: deny writeable mappings when implying SEAL_WRITE

  • Red Hat CodeReady Linux Builder EUS (v.9.6) libperf 5.14.0-570.141.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.141.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.141.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.141.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.141.1.el9_6
    fixed: vendor fix RHSA-2026:67720
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.41.1.el9_8, perf 5.14.0-687.41.1.el9_8, rtla 5.14.0-687.41.1.el9_8, python3-perf 5.14.0-687.41.1.el9_8, kernel-devel-matched 5.14.0-687.41.1.el9_8, kernel-64k-devel-matched 5.14.0-687.41.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:57252
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.49.1.el10_2, perf 6.12.0-211.49.1.el10_2, rtla 6.12.0-211.49.1.el10_2, python3-perf 6.12.0-211.49.1.el10_2, kernel-devel-matched 6.12.0-211.49.1.el10_2, kernel-64k-devel-matched 6.12.0-211.49.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:57251
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) rv 6.12.0-55.105.1.el10_0, perf 6.12.0-55.105.1.el10_0, rtla 6.12.0-55.105.1.el10_0, python3-perf 6.12.0-55.105.1.el10_0, kernel-devel-matched 6.12.0-55.105.1.el10_0, kernel-64k-devel-matched 6.12.0-55.105.1.el10_0, +7 more
    fixed: vendor fix RHSA-2026:69089
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) rv 5.14.0-570.141.1.el9_6, perf 5.14.0-570.141.1.el9_6, rtla 5.14.0-570.141.1.el9_6, python3-perf 5.14.0-570.141.1.el9_6, kernel-devel-matched 5.14.0-570.141.1.el9_6, kernel-64k-devel-matched 5.14.0-570.141.1.el9_6, +7 more
    fixed: vendor fix RHSA-2026:67720
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.41.1.el9_8, kernel-64k 5.14.0-687.41.1.el9_8, kernel-core 5.14.0-687.41.1.el9_8, kernel-tools 5.14.0-687.41.1.el9_8, kernel-modules 5.14.0-687.41.1.el9_8, kernel-64k-core 5.14.0-687.41.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:57252
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.49.1.el10_2, kernel-64k 6.12.0-211.49.1.el10_2, kernel-core 6.12.0-211.49.1.el10_2, kernel-tools 6.12.0-211.49.1.el10_2, kernel-modules 6.12.0-211.49.1.el10_2, kernel-64k-core 6.12.0-211.49.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:57251
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) kernel 6.12.0-55.105.1.el10_0, kernel-64k 6.12.0-55.105.1.el10_0, kernel-core 6.12.0-55.105.1.el10_0, kernel-tools 6.12.0-55.105.1.el10_0, kernel-modules 6.12.0-55.105.1.el10_0, kernel-64k-core 6.12.0-55.105.1.el10_0, +27 more
    fixed: vendor fix RHSA-2026:69089
show 13 more
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6) kernel 5.14.0-570.141.1.el9_6, kernel-64k 5.14.0-570.141.1.el9_6, kernel-core 5.14.0-570.141.1.el9_6, kernel-tools 5.14.0-570.141.1.el9_6, kernel-modules 5.14.0-570.141.1.el9_6, kernel-64k-core 5.14.0-570.141.1.el9_6, +27 more
    fixed: vendor fix RHSA-2026:67720
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.41.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.41.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.41.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.41.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.41.1.el9_8
    fixed: vendor fix RHSA-2026:57252
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.49.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.49.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.49.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.49.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.49.1.el10_2
    fixed: vendor fix RHSA-2026:57251
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) libperf 6.12.0-55.105.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.105.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.105.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.105.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.105.1.el10_0
    fixed: vendor fix RHSA-2026:69089
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.41.1.el9_8, kernel-rt-64k 5.14.0-687.41.1.el9_8, kernel-rt-core 5.14.0-687.41.1.el9_8, kernel-rt-modules 5.14.0-687.41.1.el9_8, kernel-rt-64k-core 5.14.0-687.41.1.el9_8, kernel-rt-debug-core 5.14.0-687.41.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:57252
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.49.1.el10_2, kernel-rt-64k 6.12.0-211.49.1.el10_2, kernel-rt-core 6.12.0-211.49.1.el10_2, kernel-rt-modules 6.12.0-211.49.1.el10_2, kernel-rt-64k-core 6.12.0-211.49.1.el10_2, kernel-rt-debug-core 6.12.0-211.49.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:57251
  • Red Hat Enterprise Linux Real Time EUS (v. 10.0) kernel-rt 6.12.0-55.105.1.el10_0, kernel-rt-64k 6.12.0-55.105.1.el10_0, kernel-rt-core 6.12.0-55.105.1.el10_0, kernel-rt-modules 6.12.0-55.105.1.el10_0, kernel-rt-64k-core 6.12.0-55.105.1.el10_0, kernel-rt-debug-core 6.12.0-55.105.1.el10_0, +14 more
    fixed: vendor fix RHSA-2026:69089
  • Red Hat Enterprise Linux Real Time EUS (v.9.6) kernel-rt 5.14.0-570.141.1.el9_6, kernel-rt-64k 5.14.0-570.141.1.el9_6, kernel-rt-core 5.14.0-570.141.1.el9_6, kernel-rt-modules 5.14.0-570.141.1.el9_6, kernel-rt-64k-core 5.14.0-570.141.1.el9_6, kernel-rt-debug-core 5.14.0-570.141.1.el9_6, +14 more
    fixed: vendor fix RHSA-2026:67720
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.41.1.el9_8, kernel-rt-core 5.14.0-687.41.1.el9_8, kernel-rt-modules 5.14.0-687.41.1.el9_8, kernel-rt-debug-core 5.14.0-687.41.1.el9_8, kernel-rt-modules-core 5.14.0-687.41.1.el9_8, kernel-rt-debug-modules 5.14.0-687.41.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:57252
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.49.1.el10_2, kernel-rt-core 6.12.0-211.49.1.el10_2, kernel-rt-modules 6.12.0-211.49.1.el10_2, kernel-rt-debug-core 6.12.0-211.49.1.el10_2, kernel-rt-modules-core 6.12.0-211.49.1.el10_2, kernel-rt-debug-modules 6.12.0-211.49.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:57251
  • Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0) kernel-rt 6.12.0-55.105.1.el10_0, kernel-rt-kvm 6.12.0-55.105.1.el10_0, kernel-rt-core 6.12.0-55.105.1.el10_0, kernel-rt-modules 6.12.0-55.105.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.105.1.el10_0, kernel-rt-debug-core 6.12.0-55.105.1.el10_0, +6 more
    fixed: vendor fix RHSA-2026:69089
  • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6) kernel-rt 5.14.0-570.141.1.el9_6, kernel-rt-kvm 5.14.0-570.141.1.el9_6, kernel-rt-core 5.14.0-570.141.1.el9_6, kernel-rt-modules 5.14.0-570.141.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.141.1.el9_6, kernel-rt-debug-core 5.14.0-570.141.1.el9_6, +6 more
    fixed: vendor fix RHSA-2026:67720
  • 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
no
Technical impact
total
Assessed
26d ago

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 8.4 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
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.