CVE-2025-68211

Aliases:UBUNTU-CVE-2025-68211DEBIAN-CVE-2025-68211
Advisory lineage Upstream: 0 Downstream: 31
Analyzed
Published: 16 Dec 2025, 13:48
Last modified:11 Jun 2026, 18:44

Vulnerability Summary

Overall Risk (default)
low
22/100
CVSS Score
5.5 MEDIUM
v3.1 (nvd)
EPSS Score
0.15% LOW
0% probability +0.12%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

16 Dec 2025, 13:48
Published
Vulnerability first disclosed
11 Jun 2026, 18:44
Last Modified
Vulnerability information updated

Description

In the Linux kernel, the following vulnerability has been resolved: ksm: use range-walk function to jump over holes in scan_get_next_rmap_item Currently, scan_get_next_rmap_item() walks every page address in a VMA to locate mergeable pages. This becomes highly inefficient when scanning large virtual memory areas that contain mostly unmapped regions, causing ksmd to use large amount of cpu without deduplicating much pages. This patch replaces the per-address lookup with a range walk using walk_page_range(). The range walker allows KSM to skip over entire unmapped holes in a VMA, avoiding unnecessary lookups. This problem was previously discussed in [1]. Consider the following test program which creates a 32 TiB mapping in the virtual address space but only populates a single page: #include <unistd.h> #include <stdio.h> #include <sys/mman.h> /* 32 TiB */ const size_t size = 32ul * 1024 * 1024 * 1024 * 1024; int main() { char *area = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0); if (area == MAP_FAILED) { perror("mmap() failed\n"); return -1; } /* Populate a single page such that we get an anon_vma. */ *area = 0; /* Enable KSM. */ madvise(area, size, MADV_MERGEABLE); pause(); return 0; } $ ./ksm-sparse & $ echo 1 > /sys/kernel/mm/ksm/run Without this patch ksmd uses 100% of the cpu for a long time (more then 1 hour in my test machine) scanning all the 32 TiB virtual address space that contain only one mapped page. This makes ksmd essentially deadlocked not able to deduplicate anything of value. With this patch ksmd walks only the one mapped page and skips the rest of the 32 TiB virtual address space, making the scan fast using little cpu.

CVSS Metrics

  • v3.1•MEDIUM•Score: 5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS Trends

Current EPSS score: 0.15%• Percentile: 4%

Affected Systems

  • debian•linux

    < 5.10.249-1 | < 6.1.162-1 | < 6.12.63-1 | < 6.17.9-1

  • debian•linux-6.1

    < 6.1.162-1~deb11u1

  • ubuntu•linux

    all | < 5.15.0-176.186 | all | < 6.17.0-14.14

  • ubuntu•linux-allwinner-5.19

    all

  • ubuntu•linux-aws

    all | < 5.15.0-1105.112 | all | < 6.17.0-1007.7

  • ubuntu•linux-aws-5.0

    all

  • ubuntu•linux-aws-5.11

    all

  • ubuntu•linux-aws-5.13

    all

  • ubuntu•linux-aws-5.15

    < 5.15.0-1105.112~20.04.1

  • ubuntu•linux-aws-5.19

    all

  • ubuntu•linux-aws-5.3

    all

  • ubuntu•linux-aws-5.4

    all

  • ubuntu•linux-aws-5.8

    all

  • ubuntu•linux-aws-6.14

    all

  • ubuntu•linux-aws-6.17

    < 6.17.0-1007.7~24.04.1

  • ubuntu•linux-aws-6.2

    all

  • ubuntu•linux-aws-6.5

    all

  • ubuntu•linux-aws-6.8

    all

  • ubuntu•linux-aws-fips

    all | < 5.15.0-1105.112+fips1

  • ubuntu•linux-aws-hwe

    all

  • ubuntu•linux-azure

    all | all | < 5.15.0-1110.119 | all | < 6.17.0-1008.8

  • ubuntu•linux-azure-4.15

    all

  • ubuntu•linux-azure-5.11

    all

  • ubuntu•linux-azure-5.13

    all

  • ubuntu•linux-azure-5.15

    < 5.15.0-1110.119~20.04.1

  • ubuntu•linux-azure-5.19

    all

  • ubuntu•linux-azure-5.3

    all

  • ubuntu•linux-azure-5.4

    all

  • ubuntu•linux-azure-5.8

    all

  • ubuntu•linux-azure-6.11

    all

  • ubuntu•linux-azure-6.14

    all

  • ubuntu•linux-azure-6.2

    all

  • ubuntu•linux-azure-6.5

    all

  • ubuntu•linux-azure-6.8

    all

  • ubuntu•linux-azure-edge

    all

  • ubuntu•linux-azure-fde

    all | all | all | all

  • ubuntu•linux-azure-fde-5.19

    all

  • ubuntu•linux-azure-fde-6.14

    all

  • ubuntu•linux-azure-fde-6.17

    all

  • ubuntu•linux-azure-fde-6.2

    all

  • ubuntu•linux-azure-fde-6.8

    all

  • ubuntu•linux-azure-fips

    all | < 5.15.0-1110.119+fips1

  • ubuntu•linux-azure-nvidia

    all

  • ubuntu•linux-azure-nvidia-6.14

    all

  • ubuntu•linux-bluefield

    all | < 5.15.0-1089.91 | all

  • ubuntu•linux-fips

    all | < 5.15.0-176.186+fips1

  • ubuntu•linux-gcp

    all | all | < 5.15.0-1105.114 | all | < 6.17.0-1007.7

  • ubuntu•linux-gcp-4.15

    all

  • ubuntu•linux-gcp-5.11

    all

  • ubuntu•linux-gcp-5.13

    all

Showing first 50 affected entries in server-rendered view.

References (29)