Skip to content
Fencer Intel
no cvss —

CVE-2025-40009 json

fs/proc/task_mmu: check p->vec_buf for NULL

published last yr. modified 21d ago also EUVD-2025-35071

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 15%
public exploits
0
none known

Summary

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

fs/proc/task_mmu: check p->vec_buf for NULL

When the PAGEMAP_SCAN ioctl is invoked with vec_len = 0 reaches pagemap_scan_backout_range(), kernel panics with null-ptr-deref:

[ 44.936808] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 44.937797] KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] [ 44.938391] CPU: 1 UID: 0 PID: 2480 Comm: reproducer Not tainted 6.17.0-rc6 #22 PREEMPT(none) [ 44.939062] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 44.939935] RIP: 0010:pagemap_scan_thp_entry.isra.0+0x741/0xa80

<snip registers, unreliable trace>

[ 44.946828] Call Trace: [ 44.947030] <TASK> [ 44.949219] pagemap_scan_pmd_entry+0xec/0xfa0 [ 44.952593] walk_pmd_range.isra.0+0x302/0x910 [ 44.954069] walk_pud_range.isra.0+0x419/0x790 [ 44.954427] walk_p4d_range+0x41e/0x620 [ 44.954743] walk_pgd_range+0x31e/0x630 [ 44.955057] __walk_page_range+0x160/0x670 [ 44.956883] walk_page_range_mm+0x408/0x980 [ 44.958677] walk_page_range+0x66/0x90 [ 44.958984] do_pagemap_scan+0x28d/0x9c0 [ 44.961833] do_pagemap_cmd+0x59/0x80 [ 44.962484] __x64_sys_ioctl+0x18d/0x210 [ 44.962804] do_syscall_64+0x5b/0x290 [ 44.963111] entry_SYSCALL_64_after_hwframe+0x76/0x7e

vec_len = 0 in pagemap_scan_init_bounce_buffer() means no buffers are allocated and p->vec_buf remains set to NULL.

This breaks an assumption made later in pagemap_scan_backout_range(), that page_region is always allocated for p->vec_buf_index.

Fix it by explicitly checking p->vec_buf for NULL before dereferencing.

Other sites that might run into same deref-issue are already (directly or transitively) protected by checking p->vec_buf.

Note: From PAGEMAP_SCAN man page, it seems vec_len = 0 is valid when no output is requested and it's only the side effects caller is interested in, hence it passes check in pagemap_scan_get_args().

This issue was found by syzkaller.

Patch / fix

  • Linux Linux 6.12.50, 6.16.10, 6.17
  • linux Debian 13 6.12.57-1
  • linux Debian 14 6.16.10-1

debian advisories DEBIAN-CVE-2025-40009

  • linux Ubuntu 24.04 LTS 6.8.0-106.106
  • linux Ubuntu 25.10 6.17.0-6.6
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1050.53
  • linux-aws Ubuntu 25.10 6.17.0-1003.3
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1052.55
  • linux-gcp Ubuntu 25.10 6.17.0-1003.3
  • 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-2025-40009

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 Linux Micro 6.2 6.12.0-160000.7.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.7.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.7.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.7.1
  • kernel-default-base SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.6.1.160000.2.4
  • kernel-syms SLES 16.0, Linux Micro Extras 6.2, SLES for SAP applications 16.0 6.12.0-160000.7.1
  • kernel-obs-qa SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.7.1
  • kernel-kvmsmall SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.7.1

suse advisories SUSE-SU-2025:21080-1SUSE-SU-2025:21147-1SUSE-SU-2025:21180-1SUSE-SU-2026:20561-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.7.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.7.1
  • kernel-kvmsmall openSUSE Leap 16.0 6.12.0-160000.7.1

opensuse advisories openSUSE-SU-2025:20091-1

Is CVE-2025-40009 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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-2025-40009 updated cvss 5.5

kernel: fs/proc/task_mmu: check p->vec_buf for NULL

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”
  • 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 rv, perf, rtla, kernel, bpftool, libperf, +83 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

0.24% chance of exploitation in the next 30 days, higher than 15% of all scored CVEs (FIRST EPSS, 2026-11-09).

Affected products

  • Linux Linux

Classification

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.