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no cvss —

CVE-2026-68086 json

mm/khugepaged: write all dirty file folios when collapsing

published 2026-08-10 2 mo ago modified 2026-11-06 2 d ago also EUVD-2026-55267

cvss
—
not scored
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:

mm/khugepaged: write all dirty file folios when collapsing

[There is no upstream commit, as this code was removed by upstream commit 044925f9b565 ("mm: fs: remove filemap_nr_thps*() functions and their users")]

As-is, khugepaged and writable-file opening exclude each other. A file cannot be open writeable and have THPs (because the filesystem is not aware of them). khugepaged will never collapse file pages for files that are opened writeable. On an open(O_RDWR/O_WRONLY), the page cache for that particular file is dropped. This is fine because nothing could've been dirtied.

However, there is an edge-case: collapse_file() might not be able to coexist with concurrent writers, but it can coexist with dirty folios (from previous writers). Therefore, the following can happen:

open(file, O_RDWR) write(file) close(file) madvise(file_mapping, MADV_COLLAPSE, some non-dirty range) open(file, O_RDWR) nr_thps > 0 truncate_inode_pages() /* THPs are cleared out, but so are the dirty folios */

When this edge-case happens, there is data loss, as the dirty folios are fully discarded.

Fix it by fully writing back the page cache (and waiting) when collapsing file THPs. Doing so provides the guarantee that no dirty folio will be observed while there are active THPs. To fully ensure this is safe, the invalidate_lock needs to be held while doing the writeout, so that do_dentry_open()'s page cache truncation excludes this write-and-wait.

As a side effect, move the nr_thps counter bumping outside the i_pages lock. This is correct since the counter itself is an atomic_t and the producer <-> consumer correctness is provided by a full memory barrier: smp_mb() in collapse_file()/memory barrier implied by full ordering in get_write_access() -> atomic_inc_unless_negative().

Patch / fix

  • Linux Linux 7.1.4
  • linux Debian 14 7.1.4-1

debian advisories DEBIAN-CVE-2026-68086

  • kernel RHEL 9 5.14.0-687.47.1.el9_8
  • rv RHEL 9 5.14.0-687.47.1.el9_8
  • perf RHEL 9 5.14.0-687.47.1.el9_8
  • rtla RHEL 9 5.14.0-687.47.1.el9_8
  • libperf RHEL 9 5.14.0-687.47.1.el9_8
  • kernel-rt RHEL 9 5.14.0-687.47.1.el9_8
  • kernel-64k RHEL 9 5.14.0-687.47.1.el9_8
  • kernel-core RHEL 9 5.14.0-687.47.1.el9_8

red hat advisories RHSA-2026:83707RHSA-2026:67150RHSA-2026:61887

  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.81.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.81.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1.150700.17.45.1

suse advisories SUSE-SU-2026:4254-1SUSE-SU-2026:23887-1SUSE-SU-2026:23902-1SUSE-SU-2026:23897-1SUSE-SU-2026:23881-1SUSE-SU-2026:4120-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.38.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.38.1

opensuse advisories openSUSE-SU-2026:21910-1

  • kernel AlmaLinux 9 5.14.0-687.47.1.el9_8
  • rv AlmaLinux 9 5.14.0-687.47.1.el9_8
  • perf AlmaLinux 9 5.14.0-687.47.1.el9_8
  • rtla AlmaLinux 9 5.14.0-687.47.1.el9_8
  • libperf AlmaLinux 9 5.14.0-687.47.1.el9_8
  • kernel-rt AlmaLinux 9 5.14.0-687.47.1.el9_8
  • kernel-64k AlmaLinux 9 5.14.0-687.47.1.el9_8
  • kernel-core AlmaLinux 9 5.14.0-687.47.1.el9_8

almalinux advisories ALSA-2026:67150ALSA-2026:61887

  • kernel Rocky Linux 9 5.14.0-687.47.1.el9_8
  • kernel Rocky Linux 10 6.12.0-211.50.1.el10_2

rocky linux advisories RLSA-2026:67150RLSA-2026:61887

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-2026-68086 updated cvss 4.7

kernel: mm/khugepaged: write all dirty file folios when collapsing

  • 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
    affected: workaround, no fix available
  • Red Hat CodeReady Linux Builder EUS (v.9.6) libperf 5.14.0-570.152.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.152.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.152.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.152.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.152.1.el9_6
    fixed: vendor fix RHSA-2026:91492
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.47.1.el9_8, perf 5.14.0-687.47.1.el9_8, rtla 5.14.0-687.47.1.el9_8, python3-perf 5.14.0-687.47.1.el9_8, kernel-devel-matched 5.14.0-687.47.1.el9_8, kernel-64k-devel-matched 5.14.0-687.47.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:67150
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.50.1.el10_2, perf 6.12.0-211.50.1.el10_2, rtla 6.12.0-211.50.1.el10_2, python3-perf 6.12.0-211.50.1.el10_2, kernel-devel-matched 6.12.0-211.50.1.el10_2, kernel-64k-devel-matched 6.12.0-211.50.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) rv 6.12.0-55.111.1.el10_0, perf 6.12.0-55.111.1.el10_0, rtla 6.12.0-55.111.1.el10_0, python3-perf 6.12.0-55.111.1.el10_0, kernel-devel-matched 6.12.0-55.111.1.el10_0, kernel-64k-devel-matched 6.12.0-55.111.1.el10_0, +7 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) rv 5.14.0-570.152.1.el9_6, perf 5.14.0-570.152.1.el9_6, rtla 5.14.0-570.152.1.el9_6, python3-perf 5.14.0-570.152.1.el9_6, kernel-devel-matched 5.14.0-570.152.1.el9_6, kernel-64k-devel-matched 5.14.0-570.152.1.el9_6, +7 more
    fixed: vendor fix RHSA-2026:91492
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.47.1.el9_8, kernel-64k 5.14.0-687.47.1.el9_8, kernel-core 5.14.0-687.47.1.el9_8, kernel-tools 5.14.0-687.47.1.el9_8, kernel-modules 5.14.0-687.47.1.el9_8, kernel-64k-core 5.14.0-687.47.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:67150
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.50.1.el10_2, kernel-64k 6.12.0-211.50.1.el10_2, kernel-core 6.12.0-211.50.1.el10_2, kernel-tools 6.12.0-211.50.1.el10_2, kernel-modules 6.12.0-211.50.1.el10_2, kernel-64k-core 6.12.0-211.50.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:61887
show 14 more
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) kernel 6.12.0-55.111.1.el10_0, kernel-64k 6.12.0-55.111.1.el10_0, kernel-core 6.12.0-55.111.1.el10_0, kernel-tools 6.12.0-55.111.1.el10_0, kernel-modules 6.12.0-55.111.1.el10_0, kernel-64k-core 6.12.0-55.111.1.el10_0, +27 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6) kernel 5.14.0-570.152.1.el9_6, kernel-64k 5.14.0-570.152.1.el9_6, kernel-core 5.14.0-570.152.1.el9_6, kernel-tools 5.14.0-570.152.1.el9_6, kernel-modules 5.14.0-570.152.1.el9_6, kernel-64k-core 5.14.0-570.152.1.el9_6, +27 more
    fixed: vendor fix RHSA-2026:91492
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.47.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.47.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.47.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.47.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.47.1.el9_8
    fixed: vendor fix RHSA-2026:67150
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.50.1.el10_2
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) libperf 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.111.1.el10_0
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.47.1.el9_8, kernel-rt-64k 5.14.0-687.47.1.el9_8, kernel-rt-core 5.14.0-687.47.1.el9_8, kernel-rt-modules 5.14.0-687.47.1.el9_8, kernel-rt-64k-core 5.14.0-687.47.1.el9_8, kernel-rt-debug-core 5.14.0-687.47.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:67150
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-64k 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-64k-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux Real Time EUS (v. 10.0) kernel-rt 6.12.0-55.111.1.el10_0, kernel-rt-64k 6.12.0-55.111.1.el10_0, kernel-rt-core 6.12.0-55.111.1.el10_0, kernel-rt-modules 6.12.0-55.111.1.el10_0, kernel-rt-64k-core 6.12.0-55.111.1.el10_0, kernel-rt-debug-core 6.12.0-55.111.1.el10_0, +14 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux Real Time EUS (v.9.6) kernel-rt 5.14.0-570.152.1.el9_6, kernel-rt-64k 5.14.0-570.152.1.el9_6, kernel-rt-core 5.14.0-570.152.1.el9_6, kernel-rt-modules 5.14.0-570.152.1.el9_6, kernel-rt-64k-core 5.14.0-570.152.1.el9_6, kernel-rt-debug-core 5.14.0-570.152.1.el9_6, +14 more
    fixed: vendor fix RHSA-2026:91492
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.47.1.el9_8, kernel-rt-core 5.14.0-687.47.1.el9_8, kernel-rt-modules 5.14.0-687.47.1.el9_8, kernel-rt-debug-core 5.14.0-687.47.1.el9_8, kernel-rt-modules-core 5.14.0-687.47.1.el9_8, kernel-rt-debug-modules 5.14.0-687.47.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:67150
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, kernel-rt-modules-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-modules 6.12.0-211.50.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0) kernel-rt 6.12.0-55.111.1.el10_0, kernel-rt-kvm 6.12.0-55.111.1.el10_0, kernel-rt-core 6.12.0-55.111.1.el10_0, kernel-rt-modules 6.12.0-55.111.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.111.1.el10_0, kernel-rt-debug-core 6.12.0-55.111.1.el10_0, +6 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6) kernel-rt 5.14.0-570.152.1.el9_6, kernel-rt-kvm 5.14.0-570.152.1.el9_6, kernel-rt-core 5.14.0-570.152.1.el9_6, kernel-rt-modules 5.14.0-570.152.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.152.1.el9_6, kernel-rt-debug-core 5.14.0-570.152.1.el9_6, +6 more
    fixed: vendor fix RHSA-2026:91492
  • 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
no
Technical impact
partial
Assessed
2 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).

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.