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CVE-2025-40237 json

fs/notify: call exportfs_encode_fid with s_umount

published 11mo ago modified 21d ago also EUVD-2025-201222

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 12%
public exploits
0
none known

Summary

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

fs/notify: call exportfs_encode_fid with s_umount

Calling intotify_show_fdinfo() on fd watching an overlayfs inode, while the overlayfs is being unmounted, can lead to dereferencing NULL ptr.

This issue was found by syzkaller.

Race Condition Diagram:

Thread 1 Thread 2 -------- --------

generic_shutdown_super() shrink_dcache_for_umount sb->s_root = NULL

| | vfs_read() | inotify_fdinfo() | * inode get from mark * | show_mark_fhandle(m, inode) | exportfs_encode_fid(inode, ..) | ovl_encode_fh(inode, ..) | ovl_check_encode_origin(inode) | * deref i_sb->s_root * | | v fsnotify_sb_delete(sb)

Which then leads to:

[ 32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] [ 32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none)

<snip registers, unreliable trace>

[ 32.143353] Call Trace: [ 32.143732] ovl_encode_fh+0xd5/0x170 [ 32.144031] exportfs_encode_inode_fh+0x12f/0x300 [ 32.144425] show_mark_fhandle+0xbe/0x1f0 [ 32.145805] inotify_fdinfo+0x226/0x2d0 [ 32.146442] inotify_show_fdinfo+0x1c5/0x350 [ 32.147168] seq_show+0x530/0x6f0 [ 32.147449] seq_read_iter+0x503/0x12a0 [ 32.148419] seq_read+0x31f/0x410 [ 32.150714] vfs_read+0x1f0/0x9e0 [ 32.152297] ksys_read+0x125/0x240

IOW ovl_check_encode_origin derefs inode->i_sb->s_root, after it was set to NULL in the unmount path.

Fix it by protecting calling exportfs_encode_fid() from show_mark_fhandle() with s_umount lock.

This form of fix was suggested by Amir in [1].

[1]: https://lore.kernel.org/all/CAOQ4uxhbDwhb+2Brs1UdkoF0a3NSdBAOQPNfEHjahrgoKJpLEw@mail.gmail.com/

Patch / fix

  • Linux Linux 6.6.73, 6.6.115, 6.12.56, 6.17.6, 6.18
  • linux Debian 13 6.12.57-1
  • linux Debian 14 6.17.6-1

debian advisories DEBIAN-CVE-2025-40237

  • linux Ubuntu 24.04 LTS 6.8.0-106.106
  • linux Ubuntu 25.10 6.17.0-14.14
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1050.53
  • linux-aws Ubuntu 25.10 6.17.0-1007.7
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1052.55
  • linux-gcp Ubuntu 25.10 6.17.0-1007.7
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1048.53
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1049.49

ubuntu advisories UBUNTU-CVE-2025-40237

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 10.2 6.12.0-211.39.1.el10_2
  • rv RHEL 10.2 6.12.0-211.39.1.el10_2
  • perf RHEL 10.2 6.12.0-211.39.1.el10_2
  • rtla RHEL 10.2 6.12.0-211.39.1.el10_2
  • libperf RHEL 10.2 6.12.0-211.39.1.el10_2
  • kernel-rt RHEL 10.2 6.12.0-211.39.1.el10_2
  • kernel-64k RHEL 10.2 6.12.0-211.39.1.el10_2
  • kernel-core RHEL 10.2 6.12.0-211.39.1.el10_2

red hat advisories RHSA-2026:77634RHSA-2026:45114

  • kernel-rt Linux Micro 6.2 6.12.0-160000.9.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.9.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.9.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.9.1
  • kernel-default-base SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.9.1.160000.2.6
  • kernel-syms SLES 16.0, Linux Micro Extras 6.2, SLES for SAP applications 16.0 6.12.0-160000.9.1
  • kernel-azure SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.9.1
  • kernel-obs-qa SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.9.1

suse advisories SUSE-SU-2026:20207-1SUSE-SU-2026:20220-1SUSE-SU-2026:20564-1SUSE-SU-2026:20228-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.9.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.9.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.9.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.9.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.9.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.9.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.9.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.9.1

opensuse advisories openSUSE-SU-2026:20145-1

  • kernel AlmaLinux 10 6.12.0-211.39.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.39.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.39.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.39.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.39.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.39.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.39.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.39.1.el10_2

almalinux advisories ALSA-2026:45114

  • kernel Rocky Linux 10 6.12.0-211.39.1.el10_2

rocky linux advisories RLSA-2026:45114

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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-2025-40237 updated cvss 5.8

kernel: fs/notify: call exportfs_encode_fid with s_umount

  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.39.1.el10_2, perf 6.12.0-211.39.1.el10_2, rtla 6.12.0-211.39.1.el10_2, python3-perf 6.12.0-211.39.1.el10_2, kernel-devel-matched 6.12.0-211.39.1.el10_2, kernel-64k-devel-matched 6.12.0-211.39.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:45114
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) rv 6.12.0-55.109.1.el10_0, perf 6.12.0-55.109.1.el10_0, rtla 6.12.0-55.109.1.el10_0, python3-perf 6.12.0-55.109.1.el10_0, kernel-devel-matched 6.12.0-55.109.1.el10_0, kernel-64k-devel-matched 6.12.0-55.109.1.el10_0, +7 more
    fixed: vendor fix RHSA-2026:77634
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.39.1.el10_2, kernel-64k 6.12.0-211.39.1.el10_2, kernel-core 6.12.0-211.39.1.el10_2, kernel-tools 6.12.0-211.39.1.el10_2, kernel-modules 6.12.0-211.39.1.el10_2, kernel-64k-core 6.12.0-211.39.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:45114
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) kernel 6.12.0-55.109.1.el10_0, kernel-64k 6.12.0-55.109.1.el10_0, kernel-core 6.12.0-55.109.1.el10_0, kernel-tools 6.12.0-55.109.1.el10_0, kernel-modules 6.12.0-55.109.1.el10_0, kernel-64k-core 6.12.0-55.109.1.el10_0, +27 more
    fixed: vendor fix RHSA-2026:77634
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.39.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.39.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.39.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.39.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.39.1.el10_2
    fixed: vendor fix RHSA-2026:45114
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) libperf 6.12.0-55.109.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.109.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.109.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.109.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.109.1.el10_0
    fixed: vendor fix RHSA-2026:77634
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.39.1.el10_2, kernel-rt-64k 6.12.0-211.39.1.el10_2, kernel-rt-core 6.12.0-211.39.1.el10_2, kernel-rt-modules 6.12.0-211.39.1.el10_2, kernel-rt-64k-core 6.12.0-211.39.1.el10_2, kernel-rt-debug-core 6.12.0-211.39.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:45114
show 4 more
  • Red Hat Enterprise Linux Real Time EUS (v. 10.0) kernel-rt 6.12.0-55.109.1.el10_0, kernel-rt-64k 6.12.0-55.109.1.el10_0, kernel-rt-core 6.12.0-55.109.1.el10_0, kernel-rt-modules 6.12.0-55.109.1.el10_0, kernel-rt-64k-core 6.12.0-55.109.1.el10_0, kernel-rt-debug-core 6.12.0-55.109.1.el10_0, +14 more
    fixed: vendor fix RHSA-2026:77634
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.39.1.el10_2, kernel-rt-core 6.12.0-211.39.1.el10_2, kernel-rt-modules 6.12.0-211.39.1.el10_2, kernel-rt-debug-core 6.12.0-211.39.1.el10_2, kernel-rt-modules-core 6.12.0-211.39.1.el10_2, kernel-rt-debug-modules 6.12.0-211.39.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:45114
  • Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0) kernel-rt 6.12.0-55.109.1.el10_0, kernel-rt-kvm 6.12.0-55.109.1.el10_0, kernel-rt-core 6.12.0-55.109.1.el10_0, kernel-rt-modules 6.12.0-55.109.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.109.1.el10_0, kernel-rt-debug-core 6.12.0-55.109.1.el10_0, +6 more
    fixed: vendor fix RHSA-2026:77634
  • 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
    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

Exploit prediction

0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-09).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

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