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Fencer Vulns
no cvss —

CVE-2025-68198 json

crash: fix crashkernel resource shrink

published 2025-12-16 10 mo ago modified 2026-10-14 26 d ago also EUVD-2025-203698

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 9%
public exploits
0
none known

Summary

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

crash: fix crashkernel resource shrink

When crashkernel is configured with a high reservation, shrinking its value below the low crashkernel reservation causes two issues:

1. Invalid crashkernel resource objects 2. Kernel crash if crashkernel shrinking is done twice

For example, with crashkernel=200M,high, the kernel reserves 200MB of high memory and some default low memory (say 256MB). The reservation appears as:

cat /proc/iomem | grep -i crash af000000-beffffff : Crash kernel 433000000-43f7fffff : Crash kernel

If crashkernel is then shrunk to 50MB (echo 52428800 > /sys/kernel/kexec_crash_size), /proc/iomem still shows 256MB reserved: af000000-beffffff : Crash kernel

Instead, it should show 50MB: af000000-b21fffff : Crash kernel

Further shrinking crashkernel to 40MB causes a kernel crash with the following trace (x86):

BUG: kernel NULL pointer dereference, address: 0000000000000038 PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI <snip...> Call Trace: <TASK> ? __die_body.cold+0x19/0x27 ? page_fault_oops+0x15a/0x2f0 ? search_module_extables+0x19/0x60 ? search_bpf_extables+0x5f/0x80 ? exc_page_fault+0x7e/0x180 ? asm_exc_page_fault+0x26/0x30 ? __release_resource+0xd/0xb0 release_resource+0x26/0x40 __crash_shrink_memory+0xe5/0x110 crash_shrink_memory+0x12a/0x190 kexec_crash_size_store+0x41/0x80 kernfs_fop_write_iter+0x141/0x1f0 vfs_write+0x294/0x460 ksys_write+0x6d/0xf0 <snip...>

This happens because __crash_shrink_memory()/kernel/crash_core.c incorrectly updates the crashk_res resource object even when crashk_low_res should be updated.

Fix this by ensuring the correct crashkernel resource object is updated when shrinking crashkernel memory.

Patch / fix

  • Linux Linux 6.6.118, 6.12.59, 6.17.9, 6.18
  • linux Debian 13 6.12.63-1
  • linux Debian 14 6.17.9-1

debian advisories DEBIAN-CVE-2025-68198

  • 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-2025-68198

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 6.12.0-160000.9.1
  • 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 Azure Linux 3.0 6.6.119.3-1

azure linux advisories AZL-72442

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2025-68198 updated cvss 5.5

kernel: crash: fix crashkernel resource shrink

  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”
  • 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

0.20% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-08).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

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