{
  "schemaVersion": 1,
  "attribution": [
    {
      "source": "CISA Known Exploited Vulnerabilities",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "licence": "US government work"
    },
    {
      "source": "GitHub Advisory Database",
      "url": "https://github.com/advisories",
      "licence": "CC BY 4.0"
    },
    {
      "source": "Have I Been Pwned",
      "url": "https://haveibeenpwned.com/",
      "licence": "CC BY 4.0"
    },
    {
      "source": "CVE Program (CVE records)",
      "url": "https://www.cve.org/Legal/TermsOfUse",
      "licence": "CVE Terms of Use",
      "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.",
      "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss/",
      "licence": "free to use; FIRST requests attribution"
    }
  ],
  "record": {
    "id": "CVE-2025-68211",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2025-68211",
    "idYear": 2025,
    "status": "PUBLISHED",
    "publishedAt": "2025-12-16T13:48:37.959Z",
    "updatedAt": "2026-06-11T18:44:19.687Z",
    "importedAt": "2026-10-24T01:57:44.935Z",
    "snapshot": {
      "id": "cve_2026-10-24_midnight_baseline",
      "at": "2026-10-24T00:00:00.000Z",
      "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"
    },
    "facts": {
      "title": "ksm: use range-walk function to jump over holes in scan_get_next_rmap_item",
      "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nksm: use range-walk function to jump over holes in scan_get_next_rmap_item\n\nCurrently, scan_get_next_rmap_item() walks every page address in a VMA to\nlocate mergeable pages.  This becomes highly inefficient when scanning\nlarge virtual memory areas that contain mostly unmapped regions, causing\nksmd to use large amount of cpu without deduplicating much pages.\n\nThis patch replaces the per-address lookup with a range walk using\nwalk_page_range().  The range walker allows KSM to skip over entire\nunmapped holes in a VMA, avoiding unnecessary lookups.  This problem was\npreviously discussed in [1].\n\nConsider the following test program which creates a 32 TiB mapping in the\nvirtual address space but only populates a single page:\n\n#include <unistd.h>\n#include <stdio.h>\n#include <sys/mman.h>\n\n/* 32 TiB */\nconst size_t size = 32ul * 1024 * 1024 * 1024 * 1024;\n\nint main() {\n        char *area = mmap(NULL, size, PROT_READ | PROT_WRITE,\n                          MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0);\n\n        if (area == MAP_FAILED) {\n                perror(\"mmap() failed\\n\");\n                return -1;\n        }\n\n        /* Populate a single page such that we get an anon_vma. */\n        *area = 0;\n\n        /* Enable KSM. */\n        madvise(area, size, MADV_MERGEABLE);\n        pause();\n        return 0;\n}\n\n$ ./ksm-sparse  &\n$ echo 1 > /sys/kernel/mm/ksm/run \n\nWithout this patch ksmd uses 100% of the cpu for a long time (more then 1\nhour in my test machine) scanning all the 32 TiB virtual address space\nthat contain only one mapped page.  This makes ksmd essentially deadlocked\nnot able to deduplicate anything of value.  With this patch ksmd walks\nonly the one mapped page and skips the rest of the 32 TiB virtual address\nspace, making the scan fast using little cpu.",
      "affected": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "31dbd01f314364b70c2e026a5793a29a4da8a9dc",
              "status": "affected",
              "versionType": "git",
              "lessThan": "220cb3e425e17587f560335924cba9f16a842c64"
            },
            {
              "version": "31dbd01f314364b70c2e026a5793a29a4da8a9dc",
              "status": "affected",
              "versionType": "git",
              "lessThan": "10644e8839544dd5699c03c8fb1aeeefc41602fd"
            },
            {
              "version": "31dbd01f314364b70c2e026a5793a29a4da8a9dc",
              "status": "affected",
              "versionType": "git",
              "lessThan": "67137b715b7db28d82e4ed07a7092c2fa6ba7adb"
            },
            {
              "version": "31dbd01f314364b70c2e026a5793a29a4da8a9dc",
              "status": "affected",
              "versionType": "git",
              "lessThan": "9c2f8a9b68024e5ebb4813665845ec0a95f2eac3"
            },
            {
              "version": "31dbd01f314364b70c2e026a5793a29a4da8a9dc",
              "status": "affected",
              "versionType": "git",
              "lessThan": "74f78421c925b6d17695566f0c5941de57fd44b3"
            },
            {
              "version": "31dbd01f314364b70c2e026a5793a29a4da8a9dc",
              "status": "affected",
              "versionType": "git",
              "lessThan": "f62973e0767e4fcd6799087787fca08ca2a85b8c"
            },
            {
              "version": "31dbd01f314364b70c2e026a5793a29a4da8a9dc",
              "status": "affected",
              "versionType": "git",
              "lessThan": "f5548c318d6520d4fa3c5ed6003eeb710763cbc5"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "versions": [
            {
              "version": "2.6.32",
              "status": "affected"
            },
            {
              "version": "0",
              "status": "unaffected",
              "versionType": "semver",
              "lessThan": "2.6.32"
            },
            {
              "version": "5.10.249",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.10.*"
            },
            {
              "version": "5.15.199",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "version": "6.1.161",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "version": "6.6.121",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "version": "6.12.59",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "version": "6.17.9",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.17.*"
            },
            {
              "version": "6.18",
              "status": "unaffected",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ]
        }
      ]
    }
  }
}