{"cve":"CVE-2026-43492","nvd":{"published":"2026-05-19T12:16:18.880","modified":"2026-10-15T02:19:33.847","status":"Modified","description":"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't 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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-190"],"references":["https://git.kernel.org/stable/c/1abd50fc3cfa16fc2074a3c8c2729c50fd9d7043","https://git.kernel.org/stable/c/26d3a97ad46c7a9226ec04d4bf35bd4998a97d16","https://git.kernel.org/stable/c/2aa77a18dc7f2670497fe3ee5acbeda0b57659e5","https://git.kernel.org/stable/c/30e513e755bb381afce6fb57cdc8694136193f22","https://git.kernel.org/stable/c/6d63615c796c085b4984e3031b9fa77fffb47360"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:35:16.954578616+00:00"},"epss":{"cve":"CVE-2026-43492","score":0.00156,"percentile":0.04744,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}