CVE-2026-43492 (GCVE-0-2026-43492)
Vulnerability from cvelistv5
Published
2026-05-19 10:44
Modified
2026-06-19 11:58
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: lib/crypto: mpi: Fix integer underflow in mpi_read_raw_from_sgl() Yiming reports an integer underflow in mpi_read_raw_from_sgl() when subtracting "lzeros" from the unsigned "nbytes". For this to happen, the scatterlist "sgl" needs to occupy more bytes than the "nbytes" parameter and the first "nbytes + 1" bytes of the scatterlist must be zero. Under these conditions, the while loop iterating over the scatterlist will count more zeroes than "nbytes", subtract the number of zeroes from "nbytes" and cause the underflow. When commit 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers") originally introduced the bug, it couldn't be triggered because all callers of mpi_read_raw_from_sgl() passed a scatterlist whose length was equal to "nbytes". However since commit 63ba4d67594a ("KEYS: asymmetric: Use new crypto interface without scatterlists"), the underflow can now actually be triggered. When invoking a KEYCTL_PKEY_ENCRYPT system call with a larger "out_len" than "in_len" and filling the "in" buffer with zeroes, crypto_akcipher_sync_prep() will create an all-zero scatterlist used for both the "src" and "dst" member of struct akcipher_request and thereby fulfil the conditions to trigger the bug: sys_keyctl() keyctl_pkey_e_d_s() asymmetric_key_eds_op() software_key_eds_op() crypto_akcipher_sync_encrypt() crypto_akcipher_sync_prep() crypto_akcipher_encrypt() rsa_enc() mpi_read_raw_from_sgl() To the user this will be visible as a DoS as the kernel spins forever, causing soft lockup splats as a side effect. Fix it.
References
Impacted products
Vendor Product Version
Linux Linux Version: 2d4d1eea540b27c72488fd1914674c42473d53df
Version: 2d4d1eea540b27c72488fd1914674c42473d53df
Version: 2d4d1eea540b27c72488fd1914674c42473d53df
Version: 2d4d1eea540b27c72488fd1914674c42473d53df
Version: 2d4d1eea540b27c72488fd1914674c42473d53df
Version: 2d4d1eea540b27c72488fd1914674c42473d53df
Version: 2d4d1eea540b27c72488fd1914674c42473d53df
Version: 2d4d1eea540b27c72488fd1914674c42473d53df
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{
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          "programFiles": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nlib/crypto: mpi: Fix integer underflow in mpi_read_raw_from_sgl()\n\nYiming reports an integer underflow in mpi_read_raw_from_sgl() when\nsubtracting \"lzeros\" from the unsigned \"nbytes\".\n\nFor this to happen, the scatterlist \"sgl\" needs to occupy more bytes\nthan the \"nbytes\" parameter and the first \"nbytes + 1\" bytes of the\nscatterlist must be zero.  Under these conditions, the while loop\niterating over the scatterlist will count more zeroes than \"nbytes\",\nsubtract the number of zeroes from \"nbytes\" and cause the underflow.\n\nWhen commit 2d4d1eea540b (\"lib/mpi: Add mpi sgl helpers\") originally\nintroduced the bug, it couldn\u0027t be triggered because all callers of\nmpi_read_raw_from_sgl() passed a scatterlist whose length was equal to\n\"nbytes\".\n\nHowever since commit 63ba4d67594a (\"KEYS: asymmetric: Use new crypto\ninterface without scatterlists\"), the underflow can now actually be\ntriggered.  When invoking a KEYCTL_PKEY_ENCRYPT system call with a\nlarger \"out_len\" than \"in_len\" and filling the \"in\" buffer with zeroes,\ncrypto_akcipher_sync_prep() will create an all-zero scatterlist used for\nboth the \"src\" and \"dst\" member of struct akcipher_request and thereby\nfulfil the conditions to trigger the bug:\n\n  sys_keyctl()\n    keyctl_pkey_e_d_s()\n      asymmetric_key_eds_op()\n        software_key_eds_op()\n          crypto_akcipher_sync_encrypt()\n            crypto_akcipher_sync_prep()\n              crypto_akcipher_encrypt()\n                rsa_enc()\n                  mpi_read_raw_from_sgl()\n\nTo the user this will be visible as a DoS as the kernel spins forever,\ncausing soft lockup splats as a side effect.\n\nFix it."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-19T11:58:38.782Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a1793a48881ec8d26e9c79b0ee65753f1c6846a4"
        },
        {
          "url": "https://git.kernel.org/stable/c/1abd50fc3cfa16fc2074a3c8c2729c50fd9d7043"
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        {
          "url": "https://git.kernel.org/stable/c/6d63615c796c085b4984e3031b9fa77fffb47360"
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        {
          "url": "https://git.kernel.org/stable/c/2aa77a18dc7f2670497fe3ee5acbeda0b57659e5"
        },
        {
          "url": "https://git.kernel.org/stable/c/26d3a97ad46c7a9226ec04d4bf35bd4998a97d16"
        },
        {
          "url": "https://git.kernel.org/stable/c/8637dfb4c1d8a7026ef681f2477c6de8b71c4003"
        },
        {
          "url": "https://git.kernel.org/stable/c/30e513e755bb381afce6fb57cdc8694136193f22"
        },
        {
          "url": "https://git.kernel.org/stable/c/8c2f1288250a90a4b5cabed5d888d7e3aeed4035"
        }
      ],
      "title": "lib/crypto: mpi: Fix integer underflow in mpi_read_raw_from_sgl()",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43492",
    "datePublished": "2026-05-19T10:44:24.719Z",
    "dateReserved": "2026-05-01T14:12:56.013Z",
    "dateUpdated": "2026-06-19T11:58:38.782Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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