{"id":"CVE-2026-90199","published":"2026-09-17T17:17:14.790","lastModified":"2026-09-18T18:17:45.950","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/ntfs3: reject out-of-range evcn in mi_enum_attr()\n\nIn mi_enum_attr(), the start/end VCN validation for non-resident\nattributes is:\n\n\tif (svcn > evcn + 1) goto out;\n\nWhen evcn is U64_MAX the \"evcn + 1\" expression wraps to 0 and any svcn\npasses the check. For evcn values close to U64_MAX (but not equal to it)\nthe right-hand side is still a meaningless near-wrap upper bound, so a\nmalformed on-disk attribute with svcn == 0 and evcn near U64_MAX can pass\nmi_enum_attr() unrejected.\n\nVCN (virtual cluster number) is a cluster index, so any valid evcn is\nbounded by the volume's total cluster count, which ntfs3 holds in\nsbi->used.bitmap.nbits (set up in ntfs_init_from_boot() before any caller\nof mi_enum_attr() runs). Reject evcn values that fall outside this range.\n\nHowever, an empty non-resident attribute (no allocated clusters) is\nlegitimately encoded with svcn == 0 and evcn == -1 (U64_MAX), e.g. via\nattr->nres.evcn = cpu_to_le64((u64)vcn - 1) with vcn == 0. That sentinel\nmust keep passing, so exclude evcn == U64_MAX from the range check. The\nexisting \"svcn > evcn + 1\" test still tolerates the sentinel (\"0 > 0\" is\nfalse) and continues to require svcn == 0 for it, while the range check\nrejects every other out-of-range evcn and thereby also defuses the\n\"evcn + 1\" wraparound.\n\nsvcn does not need its own bound: once evcn < nbits, \"svcn > evcn + 1\"\nimplies svcn <= nbits.\n\n[almaz.alexandrovich@paragon-software.com: fixed evcn check]","cvssScore":7.8,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/0441e34ce098c19185a7b52c5b8b89a8a5b26888","tags":[]},{"url":"https://git.kernel.org/stable/c/20fd9f64c0050658f2031e6bd5d552c6f0c8f7e3","tags":[]},{"url":"https://git.kernel.org/stable/c/2b9a0e57bfd365e2096706b19ae34dce3b4a884b","tags":[]},{"url":"https://git.kernel.org/stable/c/7ab69cef49ebdfee288287d62641b24ab1445ecc","tags":[]},{"url":"https://git.kernel.org/stable/c/ce9a619c432b9a4044fee115c5483fbed946c131","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}