CVE-2021-47640 (GCVE-0-2021-47640)

Vulnerability from cvelistv5 – Published: 2025-02-26 01:54 – Updated: 2026-05-23 15:20
VLAI
Title
powerpc/kasan: Fix early region not updated correctly
Summary
In the Linux kernel, the following vulnerability has been resolved: powerpc/kasan: Fix early region not updated correctly The shadow's page table is not updated when PTE_RPN_SHIFT is 24 and PAGE_SHIFT is 12. It not only causes false positives but also false negative as shown the following text. Fix it by bringing the logic of kasan_early_shadow_page_entry here. 1. False Positive: ================================================================== BUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50 Write of size 16 at addr f57f3be0 by task swapper/0/1 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1 Call Trace: [c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (unreliable) [c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300 [c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200 [c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0 [c80d1cc0] [c03018a4] memset+0x34/0x90 [c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50 [c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570 [c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0 [c80d1db0] [c2036580] init_sd+0xc4/0x1d0 [c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c [c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384 [c80d1ef0] [c0004b14] kernel_init+0x24/0x170 [c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64 Memory state around the buggy address: f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 >f57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ================================================================== 2. False Negative (with KASAN tests): ================================================================== Before fix: ok 45 - kmalloc_double_kzfree # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:1039 KASAN failure expected in "((volatile char *)area)[3100]", but none occurred not ok 46 - vmalloc_oob not ok 1 - kasan ================================================================== After fix: ok 1 - kasan
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: cbd18991e24fea2c31da3bb117c83e4a3538cd11 , < 7f19245c3647afea8c7c41f795506ef70f64b9f2 (git)
Affected: cbd18991e24fea2c31da3bb117c83e4a3538cd11 , < f39a3309393a4a484532f6ba745c6acbcfe06115 (git)
Affected: cbd18991e24fea2c31da3bb117c83e4a3538cd11 , < 5a3d8f3192a409893c57808cc935e16484df1068 (git)
Affected: cbd18991e24fea2c31da3bb117c83e4a3538cd11 , < de56beace6648065d404cd9835aa7d30e3df519d (git)
Affected: cbd18991e24fea2c31da3bb117c83e4a3538cd11 , < e3d157a4b4f4e0268c98be5b7013bf4b31234bb6 (git)
Affected: cbd18991e24fea2c31da3bb117c83e4a3538cd11 , < dd75080aa8409ce10d50fb58981c6b59bf8707d3 (git)
Affected: 3822dd8c102d11ada9d9ed8e04cad0b347a04689 (git)
Affected: 5.3.6 , < 5.4 (semver)
Create a notification for this product.
Linux Linux Affected: 5.4
Unaffected: 0 , < 5.4 (semver)
Unaffected: 5.4.189 , ≤ 5.4.* (semver)
Unaffected: 5.10.110 , ≤ 5.10.* (semver)
Unaffected: 5.15.33 , ≤ 5.15.* (semver)
Unaffected: 5.16.19 , ≤ 5.16.* (semver)
Unaffected: 5.17.2 , ≤ 5.17.* (semver)
Unaffected: 5.18 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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              "lessThanOrEqual": "5.10.*",
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/kasan: Fix early region not updated correctly\n\nThe shadow\u0027s page table is not updated when PTE_RPN_SHIFT is 24\nand PAGE_SHIFT is 12. It not only causes false positives but\nalso false negative as shown the following text.\n\nFix it by bringing the logic of kasan_early_shadow_page_entry here.\n\n1. False Positive:\n==================================================================\nBUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50\nWrite of size 16 at addr f57f3be0 by task swapper/0/1\n\nCPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1\nCall Trace:\n[c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (unreliable)\n[c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300\n[c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200\n[c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0\n[c80d1cc0] [c03018a4] memset+0x34/0x90\n[c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50\n[c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570\n[c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0\n[c80d1db0] [c2036580] init_sd+0xc4/0x1d0\n[c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c\n[c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384\n[c80d1ef0] [c0004b14] kernel_init+0x24/0x170\n[c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64\n\nMemory state around the buggy address:\n f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n\u003ef57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n                                               ^\n f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n==================================================================\n\n2. False Negative (with KASAN tests):\n==================================================================\nBefore fix:\n    ok 45 - kmalloc_double_kzfree\n    # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:1039\n    KASAN failure expected in \"((volatile char *)area)[3100]\", but none occurred\n    not ok 46 - vmalloc_oob\n    not ok 1 - kasan\n\n==================================================================\nAfter fix:\n    ok 1 - kasan"
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        "dateUpdated": "2026-05-23T15:20:23.390Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "references": [
        {
          "url": "https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2"
        },
        {
          "url": "https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115"
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          "url": "https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068"
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      "title": "powerpc/kasan: Fix early region not updated correctly",
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2021-47640",
    "datePublished": "2025-02-26T01:54:12.130Z",
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    "dateUpdated": "2026-05-23T15:20:23.390Z",
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    "epss": {
      "cve": "CVE-2021-47640",
      "date": "2026-07-20",
      "epss": "0.00245",
      "percentile": "0.15741"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2021-47640\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-02-26T06:37:05.780\",\"lastModified\":\"2026-06-17T04:18:13.227\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\npowerpc/kasan: Fix early region not updated correctly\\n\\nThe shadow\u0027s page table is not updated when PTE_RPN_SHIFT is 24\\nand PAGE_SHIFT is 12. It not only causes false positives but\\nalso false negative as shown the following text.\\n\\nFix it by bringing the logic of kasan_early_shadow_page_entry here.\\n\\n1. False Positive:\\n==================================================================\\nBUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50\\nWrite of size 16 at addr f57f3be0 by task swapper/0/1\\n\\nCPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1\\nCall Trace:\\n[c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (unreliable)\\n[c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300\\n[c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200\\n[c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0\\n[c80d1cc0] [c03018a4] memset+0x34/0x90\\n[c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50\\n[c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570\\n[c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0\\n[c80d1db0] [c2036580] init_sd+0xc4/0x1d0\\n[c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c\\n[c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384\\n[c80d1ef0] [c0004b14] kernel_init+0x24/0x170\\n[c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64\\n\\nMemory state around the buggy address:\\n f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\\n f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\\n\u003ef57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\\n                                               ^\\n f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\\n f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\\n==================================================================\\n\\n2. False Negative (with KASAN tests):\\n==================================================================\\nBefore fix:\\n    ok 45 - kmalloc_double_kzfree\\n    # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:1039\\n    KASAN failure expected in \\\"((volatile char *)area)[3100]\\\", but none occurred\\n    not ok 46 - vmalloc_oob\\n    not ok 1 - kasan\\n\\n==================================================================\\nAfter fix:\\n    ok 1 - kasan\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: powerpc/kasan: Se solucion\u00f3 que la regi\u00f3n temprana no se actualizara correctamente La tabla de p\u00e1ginas de shadow no se actualiza cuando PTE_RPN_SHIFT es 24 y PAGE_SHIFT es 12. No solo causa falsos positivos sino tambi\u00e9n falsos negativos como se muestra en el siguiente texto. Arr\u00e9glelo trayendo la l\u00f3gica de kasan_early_shadow_page_entry aqu\u00ed. 1. Falso positivo: ==================================================================== ERROR: KASAN: vmalloc fuera de los l\u00edmites en pcpu_alloc+0x508/0xa50 Escritura de tama\u00f1o 16 en la direcci\u00f3n f57f3be0 por la tarea swapper/0/1 CPU: 0 PID: 1 Comm: swapper/0 No contaminado 5.15.0-12267-gdebe436e77c7 #1 Seguimiento de llamadas: [c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (no confiable) [c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300 [c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200 [c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0 [c80d1cc0] [c03018a4] memset+0x34/0x90 [c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50 [c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570 [c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0 [c80d1db0] [c2036580] init_sd+0xc4/0x1d0 [c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c [c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384 [c80d1ef0] [c0004b14] kernel_init+0x24/0x170 [c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64 Estado de la memoria alrededor de la direcci\u00f3n con errores: f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 \u0026gt;f57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ===================================================================== 2. Falso negativo (con pruebas KASAN): ==================================================================== Antes de la correcci\u00f3n: ok 45 - kmalloc_double_kzfree # vmalloc_oob: EXPECTATIVA FALL\u00d3 en lib/test_kasan.c:1039 Se esperaba una falla de KASAN en \\\"((volatile char *)area)[3100]\\\", pero no ocurri\u00f3 ninguna no ok 46 - vmalloc_oob no ok 1 - kasan ======================================================================== Despu\u00e9s de la correcci\u00f3n: ok 1 - kasan\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"arch/powerpc/mm/kasan/kasan_init_32.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"cbd18991e24fea2c31da3bb117c83e4a3538cd11\",\"lessThan\":\"7f19245c3647afea8c7c41f795506ef70f64b9f2\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"cbd18991e24fea2c31da3bb117c83e4a3538cd11\",\"lessThan\":\"f39a3309393a4a484532f6ba745c6acbcfe06115\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"cbd18991e24fea2c31da3bb117c83e4a3538cd11\",\"lessThan\":\"5a3d8f3192a409893c57808cc935e16484df1068\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"cbd18991e24fea2c31da3bb117c83e4a3538cd11\",\"lessThan\":\"de56beace6648065d404cd9835aa7d30e3df519d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"cbd18991e24fea2c31da3bb117c83e4a3538cd11\",\"lessThan\":\"e3d157a4b4f4e0268c98be5b7013bf4b31234bb6\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"cbd18991e24fea2c31da3bb117c83e4a3538cd11\",\"lessThan\":\"dd75080aa8409ce10d50fb58981c6b59bf8707d3\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"3822dd8c102d11ada9d9ed8e04cad0b347a04689\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"5.3.6\",\"lessThan\":\"5.4\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"arch/powerpc/mm/kasan/kasan_init_32.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.4\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.4\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.4.189\",\"lessThanOrEqual\":\"5.4.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.10.110\",\"lessThanOrEqual\":\"5.10.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.33\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.16.19\",\"lessThanOrEqual\":\"5.16.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.17.2\",\"lessThanOrEqual\":\"5.17.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.18\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9},{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2025-10-01T19:50:44.222623Z\",\"id\":\"CVE-2021-47640\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"total\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-787\"}]},{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-787\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.4\",\"versionEndExcluding\":\"5.4.189\",\"matchCriteriaId\":\"80DDFBB5-E7D8-4F00-9608-47CCB8D46CA4\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.5\",\"versionEndExcluding\":\"5.10.110\",\"matchCriteriaId\":\"91D3BFD0-D3F3-4018-957C-96CCBF357D79\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.11\",\"versionEndExcluding\":\"5.15.33\",\"matchCriteriaId\":\"27C42AE8-B387-43E2-938A-E1C8B40BE6D5\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.16\",\"versionEndExcluding\":\"5.16.19\",\"matchCriteriaId\":\"20C43679-0439-405A-B97F-685BEE50613B\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.17\",\"versionEndExcluding\":\"5.17.2\",\"matchCriteriaId\":\"210C679C-CF84-44A3-8939-E629C87E54BF\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-06-29T20:23:01+00:00",
      "cve": "CVE-2021-47640",
      "id": "CVE-2021-47640",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: powerpc/kasan: Fix early region not updated correctly",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47640.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 7.8, \"attackVector\": \"LOCAL\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"LOW\", \"confidentialityImpact\": \"HIGH\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2021-47640\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2025-10-01T19:50:44.222623Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-787\", \"description\": \"CWE-787 Out-of-bounds Write\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2025-10-01T16:01:44.600Z\"}}], \"cna\": {\"title\": \"powerpc/kasan: Fix early region not updated correctly\", \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"cbd18991e24fea2c31da3bb117c83e4a3538cd11\", \"lessThan\": \"7f19245c3647afea8c7c41f795506ef70f64b9f2\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"cbd18991e24fea2c31da3bb117c83e4a3538cd11\", \"lessThan\": \"f39a3309393a4a484532f6ba745c6acbcfe06115\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"cbd18991e24fea2c31da3bb117c83e4a3538cd11\", \"lessThan\": \"5a3d8f3192a409893c57808cc935e16484df1068\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"cbd18991e24fea2c31da3bb117c83e4a3538cd11\", \"lessThan\": \"de56beace6648065d404cd9835aa7d30e3df519d\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"cbd18991e24fea2c31da3bb117c83e4a3538cd11\", \"lessThan\": \"e3d157a4b4f4e0268c98be5b7013bf4b31234bb6\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"cbd18991e24fea2c31da3bb117c83e4a3538cd11\", \"lessThan\": \"dd75080aa8409ce10d50fb58981c6b59bf8707d3\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3822dd8c102d11ada9d9ed8e04cad0b347a04689\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"5.3.6\", \"lessThan\": \"5.4\", \"versionType\": \"semver\"}], \"programFiles\": [\"arch/powerpc/mm/kasan/kasan_init_32.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"5.4\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"5.4\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.4.189\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.4.*\"}, {\"status\": \"unaffected\", \"version\": \"5.10.110\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.33\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"5.16.19\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.16.*\"}, {\"status\": \"unaffected\", \"version\": \"5.17.2\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.17.*\"}, {\"status\": \"unaffected\", \"version\": \"5.18\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"arch/powerpc/mm/kasan/kasan_init_32.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2\"}, {\"url\": \"https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115\"}, {\"url\": \"https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068\"}, {\"url\": \"https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d\"}, {\"url\": \"https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6\"}, {\"url\": \"https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\npowerpc/kasan: Fix early region not updated correctly\\n\\nThe shadow\u0027s page table is not updated when PTE_RPN_SHIFT is 24\\nand PAGE_SHIFT is 12. It not only causes false positives but\\nalso false negative as shown the following text.\\n\\nFix it by bringing the logic of kasan_early_shadow_page_entry here.\\n\\n1. False Positive:\\n==================================================================\\nBUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50\\nWrite of size 16 at addr f57f3be0 by task swapper/0/1\\n\\nCPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1\\nCall Trace:\\n[c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (unreliable)\\n[c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300\\n[c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200\\n[c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0\\n[c80d1cc0] [c03018a4] memset+0x34/0x90\\n[c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50\\n[c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570\\n[c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0\\n[c80d1db0] [c2036580] init_sd+0xc4/0x1d0\\n[c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c\\n[c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384\\n[c80d1ef0] [c0004b14] kernel_init+0x24/0x170\\n[c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64\\n\\nMemory state around the buggy address:\\n f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\\n f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\\n\u003ef57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\\n                                               ^\\n f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\\n f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\\n==================================================================\\n\\n2. False Negative (with KASAN tests):\\n==================================================================\\nBefore fix:\\n    ok 45 - kmalloc_double_kzfree\\n    # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:1039\\n    KASAN failure expected in \\\"((volatile char *)area)[3100]\\\", but none occurred\\n    not ok 46 - vmalloc_oob\\n    not ok 1 - kasan\\n\\n==================================================================\\nAfter fix:\\n    ok 1 - kasan\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.189\", \"versionStartIncluding\": \"5.4\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.110\", \"versionStartIncluding\": \"5.4\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.33\", \"versionStartIncluding\": \"5.4\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.16.19\", \"versionStartIncluding\": \"5.4\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.17.2\", \"versionStartIncluding\": \"5.4\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.18\", \"versionStartIncluding\": \"5.4\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"5.3.6\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-05-23T15:20:23.390Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-47640\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-23T15:20:23.390Z\", \"dateReserved\": \"2025-02-26T01:48:21.519Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2025-02-26T01:54:12.130Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.