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CVE-2026-45990

Estado: AnalizadaMedia (5.5)—

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

slub: fix data loss and overflow in krealloc()

Commit 2cd8231796b5 ("mm/slub: allow to set node and align in k[v]realloc") introduced the ability to force a reallocation if the original object does not satisfy new alignment or NUMA node, even when the object is being shrunk.

This introduced two bugs in the reallocation fallback path:

The same overflow bug exists in the kvrealloc() fallback path, where the old bucket size ksize(p) is copied into the new buffer without being bounded by the new size.

A simple reproducer:

demonstrates the issue:

Leer descripción completaMostrar menos

Fix it by moving the old size calculation to the top of __do_krealloc() and bounding all copy lengths by the new allocation size.

Detalles técnicos trazas, registros y código del informe original
1. Data loss during NUMA migration: The jump to 'alloc_new' happens
   before 'ks' and 'orig_size' are initialized. As a result, the
   memcpy() in the 'alloc_new' block would copy 0 bytes into the new
   allocation.

2. Buffer overflow during shrinking: When shrinking an object while
   forcing a new alignment, 'new_size' is smaller than the old size.
   However, the memcpy() used the old size ('orig_size ?: ks'), leading
   to an out-of-bounds write.

	// e.g. add to lkdtm as KREALLOC_SHRINK_OVERFLOW
	while (1) {
		void *p = kmalloc(128, GFP_KERNEL);
		p = krealloc_node_align(p, 64, 256, GFP_KERNEL, NUMA_NO_NODE);
		kfree(p);
	}

  ==================================================================
  BUG: KFENCE: out-of-bounds write in memcpy_orig+0x68/0x130

  Out-of-bounds write at 0xffff8883ad757038 (120B right of kfence-#47):
   memcpy_orig+0x68/0x130
   krealloc_node_align_noprof+0x1c8/0x340
   lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm]
   lkdtm_do_action+0x3a/0x60 [lkdtm]
   ...

  kfence-#47: 0xffff8883ad756fc0-0xffff8883ad756fff, size=64, cache=kmalloc-64

  allocated by task 316 on cpu 7 at 97.680481s (0.021813s ago):
   krealloc_node_align_noprof+0x19c/0x340
   lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm]
   lkdtm_do_action+0x3a/0x60 [lkdtm]
   ...
  ==================================================================

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-45990",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.5,
          "attackVector": "LOCAL",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2cd8231796b5e7133b1c3d66ad7d2a3c42c97258",
              "lessThan": "38387ccc0fbe38d14fb4c2ad7ee1d7404e5e59fd",
              "versionType": "git"
            },
            {
              "status": "affected",
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              "lessThan": "550fa6b5aabb096554536ac1e3ec96b76cbb35fd",
              "versionType": "git"
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            {
              "status": "affected",
              "version": "2cd8231796b5e7133b1c3d66ad7d2a3c42c97258",
              "lessThan": "082a6d03a2d685a83a332666b500ad3966349588",
              "versionType": "git"
            }
          ],
          "programFiles": [
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          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.18"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "6.18",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.18.27",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.0.4",
              "versionType": "semver",
              "lessThanOrEqual": "7.0.*"
            },
            {
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "mm/slub.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-05-27T14:17:16.527",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/082a6d03a2d685a83a332666b500ad3966349588",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/38387ccc0fbe38d14fb4c2ad7ee1d7404e5e59fd",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/550fa6b5aabb096554536ac1e3ec96b76cbb35fd",
      "tags": [
        "Patch"
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-190"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nslub: fix data loss and overflow in krealloc()\n\nCommit 2cd8231796b5 (\"mm/slub: allow to set node and align in\nk[v]realloc\") introduced the ability to force a reallocation if the\noriginal object does not satisfy new alignment or NUMA node, even when\nthe object is being shrunk.\n\nThis introduced two bugs in the reallocation fallback path:\n\n1. Data loss during NUMA migration: The jump to 'alloc_new' happens\n   before 'ks' and 'orig_size' are initialized. As a result, the\n   memcpy() in the 'alloc_new' block would copy 0 bytes into the new\n   allocation.\n\n2. Buffer overflow during shrinking: When shrinking an object while\n   forcing a new alignment, 'new_size' is smaller than the old size.\n   However, the memcpy() used the old size ('orig_size ?: ks'), leading\n   to an out-of-bounds write.\n\nThe same overflow bug exists in the kvrealloc() fallback path, where the\nold bucket size ksize(p) is copied into the new buffer without being\nbounded by the new size.\n\nA simple reproducer:\n\n\t// e.g. add to lkdtm as KREALLOC_SHRINK_OVERFLOW\n\twhile (1) {\n\t\tvoid *p = kmalloc(128, GFP_KERNEL);\n\t\tp = krealloc_node_align(p, 64, 256, GFP_KERNEL, NUMA_NO_NODE);\n\t\tkfree(p);\n\t}\n\ndemonstrates the issue:\n\n  ==================================================================\n  BUG: KFENCE: out-of-bounds write in memcpy_orig+0x68/0x130\n\n  Out-of-bounds write at 0xffff8883ad757038 (120B right of kfence-#47):\n   memcpy_orig+0x68/0x130\n   krealloc_node_align_noprof+0x1c8/0x340\n   lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm]\n   lkdtm_do_action+0x3a/0x60 [lkdtm]\n   ...\n\n  kfence-#47: 0xffff8883ad756fc0-0xffff8883ad756fff, size=64, cache=kmalloc-64\n\n  allocated by task 316 on cpu 7 at 97.680481s (0.021813s ago):\n   krealloc_node_align_noprof+0x19c/0x340\n   lkdtm_KREALLOC_SHRINK_OVERFLOW+0x8c/0xc0 [lkdtm]\n   lkdtm_do_action+0x3a/0x60 [lkdtm]\n   ...\n  ==================================================================\n\nFix it by moving the old size calculation to the top of __do_krealloc()\nand bounding all copy lengths by the new allocation size."
    }
  ],
  "lastModified": "2026-06-17T10:52:51.603",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "1A10DA86-4154-4102-9D63-807CF10A4352",
              "versionEndExcluding": "6.18.27",
              "versionStartIncluding": "6.18"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "CDB78D6D-22C3-4154-B0D0-94AF1CE5C2E3",
              "versionEndExcluding": "7.0.4",
              "versionStartIncluding": "6.19"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}