CVE-2023-53474 (GCVE-0-2023-53474)
Vulnerability from cvelistv5
Published
2025-10-01 11:42
Modified
2026-08-05 09:14
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: x86/MCE/AMD: Use an u64 for bank_map Thee maximum number of MCA banks is 64 (MAX_NR_BANKS), see a0bc32b3cacf ("x86/mce: Increase maximum number of banks to 64"). However, the bank_map which contains a bitfield of which banks to initialize is of type unsigned int and that overflows when those bit numbers are >= 32, leading to UBSAN complaining correctly: UBSAN: shift-out-of-bounds in arch/x86/kernel/cpu/mce/amd.c:1365:38 shift exponent 32 is too large for 32-bit type 'int' Change the bank_map to a u64 and use the proper BIT_ULL() macro when modifying bits in there. [ bp: Rewrite commit message. ]
References
Impacted products
Vendor Product Version
Linux Linux Version: a0bc32b3cacf194dc479b342f006203fd1e1941a
Version: a0bc32b3cacf194dc479b342f006203fd1e1941a
Version: a0bc32b3cacf194dc479b342f006203fd1e1941a
Version: a0bc32b3cacf194dc479b342f006203fd1e1941a
Version: a0bc32b3cacf194dc479b342f006203fd1e1941a
Version: a0bc32b3cacf194dc479b342f006203fd1e1941a
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kernel/cpu/mce/amd.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.10"
            },
            {
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "5.10.180",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.28",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.2.*",
              "status": "unaffected",
              "version": "6.2.15",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.3.*",
              "status": "unaffected",
              "version": "6.3.2",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.4",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.180",
                  "versionStartIncluding": "5.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.111",
                  "versionStartIncluding": "5.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.28",
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                {
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                  "versionEndExcluding": "6.2.15",
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                  "versionEndExcluding": "6.4",
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                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/MCE/AMD: Use an u64 for bank_map\n\nThee maximum number of MCA banks is 64 (MAX_NR_BANKS), see\n\n  a0bc32b3cacf (\"x86/mce: Increase maximum number of banks to 64\").\n\nHowever, the bank_map which contains a bitfield of which banks to\ninitialize is of type unsigned int and that overflows when those bit\nnumbers are \u003e= 32, leading to UBSAN complaining correctly:\n\n  UBSAN: shift-out-of-bounds in arch/x86/kernel/cpu/mce/amd.c:1365:38\n  shift exponent 32 is too large for 32-bit type \u0027int\u0027\n\nChange the bank_map to a u64 and use the proper BIT_ULL() macro when\nmodifying bits in there.\n\n  [ bp: Rewrite commit message. ]"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The affected code is x86 AMD machine-check bank initialization, reached only during local CPU identification and the CPU-hotplug online callback (`mce_cpu_online()`), plus the local threshold sysfs/LVT interrupt paths. There is no network-facing or adjacent-network path, and KVM caps guests at 32 MCA banks so the condition is not reachable from a guest.\nAC:L - On an affected system (AMD CPU whose MCG_CAP reports more than 32 MCA banks, as MAX_NR_BANKS=64 was raised to support), the out-of-range shift is hit deterministically on every CPU bring-up with no race, timing window, or memory-layout dependency. Consistent with the scoring of other hardware-model-specific arch/x86/kernel/cpu defects, the platform precondition is treated as the vulnerable configuration rather than as added complexity.\nPR:L - The buggy bitmap handling executes during boot with no privileges at all, and the misprogrammed threshold banks/MSR addresses it produces are subsequently exercised through the low-privilege local surface; re-triggering it deliberately via CPU offline/online needs only local access to the machine. A basic local user is the lowest-privileged actor on such a system, so PR:L rather than PR:H.\nUI:N - The defect is triggered automatically by kernel CPU initialization and the hotplug/thresholding paths; no victim has to open a file, mount anything, or take any other action.\nS:U - The corruption is confined to the kernel\u0027s own per-CPU MCE bookkeeping and MSR programming within the same security authority. No VM, IOMMU, or sandbox boundary is crossed \u2014 the KVM MCE bank limit of 32 rules out a guest-to-host angle.\nC:H - The aliased `smca_misc_banks_map` makes `smca_get_block_address()` hand back MISCy MSR addresses for banks that have no such registers, and `allocate_threshold_blocks()` recurses over and reads those out-of-range MCA register addresses, exposing hardware state that belongs to unrelated banks through the threshold block objects. Undefined shift behaviour additionally lets the compiler assume `bank \u003c 32`, so the resulting indexing is not reliably bounded.\nI:H - `threshold_restart_bank()` performs an unguarded `wrmsr()` on the mis-derived `b-\u003eaddress`, so MCA threshold, LVT-offset and control registers of the wrong bank get overwritten, and the aliased `bank_map` enables/disables thresholding and deferred-error reporting for banks other than the intended ones. This is attacker-influenceable kernel-controlled machine state written to the wrong target.\nA:H - The same mis-derived address reaches the unguarded `rdmsr()`/`wrmsr()` in `threshold_restart_bank()`, where a non-existent MSR raises an unhandled `#GP` in kernel context and panics the machine, and with `CONFIG_UBSAN_TRAP=y` the shift-out-of-bounds itself traps during CPU bring-up. Beyond the crash, the corrupted `bank_map` breaks MCA thresholding for banks \u226532 so genuine uncorrectable hardware errors are misconfigured or unhandled."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T09:14:15.723Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a9b9ea0e63a0ec5e97bf1219ab6dcbd55e362f83"
        },
        {
          "url": "https://git.kernel.org/stable/c/11c58a0c1937c157dbdf82d5ab634d68c99f3098"
        },
        {
          "url": "https://git.kernel.org/stable/c/ba8ffb1251eb629c2ec35220e3896cf4f7b888a7"
        },
        {
          "url": "https://git.kernel.org/stable/c/9669fa17287c3af2bbd4868d4c8fdd9e57f8332e"
        },
        {
          "url": "https://git.kernel.org/stable/c/67bb7521b6420d81dab7538c0686f18f7d6d09f4"
        },
        {
          "url": "https://git.kernel.org/stable/c/4c1cdec319b9aadb65737c3eb1f5cb74bd6aa156"
        }
      ],
      "title": "x86/MCE/AMD: Use an u64 for bank_map",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2023-53474",
    "datePublished": "2025-10-01T11:42:43.798Z",
    "dateReserved": "2025-10-01T11:39:39.401Z",
    "dateUpdated": "2026-08-05T09:14:15.723Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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