{"id":"CVE-2026-72209","summary":"ntfs: validate attribute values on lookup","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nntfs: validate attribute values on lookup\n\nntfs_attr_find() and ntfs_external_attr_find() check that generic\nresident attribute values fit in their attribute records and that\nfixed-size resident values are large enough. For variable-length resident\nformats, however, the fixed part is not enough: embedded length fields\ncan still point callers past the resident value.\n\nA crafted image can set a small resident $FILE_NAME value_length while\nleaving file_name_length large. Callers then trust file_name_length and\nread past the resident value when converting or comparing the name. This\nwas reproduced with a crafted image under KASAN as a slab-out-of-bounds\nread from the kmalloc-1k MFT record copy. The stack included\nntfs_lookup(), ntfs_iget(), ntfs_read_locked_inode(), ntfs_attr_name_get(),\nntfs_ucstonls(), and utf16s_to_utf8s().\n\nAdd a shared attribute value validator and use it before a lookup path\ncan return an attribute, including the AT_UNUSED enumeration case where\ncallers inspect returned attributes directly. The helper validates\nresident value bounds, minimum resident value sizes, variable-length\n$FILE_NAME fields, and non-resident mapping-pairs metadata that was\npreviously checked separately in both lookup paths.\n\nThis also preserves the intended resident @val matching semantics in the\nexternal attribute lookup path. The old duplicated validation block\noverwrote the actual resident value length with the type-specific minimum\nlength before comparing @val, so variable-length resident values could\nfail to match even when the bytes were identical. Keep the comparison on\nthe actual value length, and make ntfs_attrlist_entry_add() compare\nresident attributes with lowest_vcn zero instead of reading the\nnon-resident union member after a successful resident match.\n\nReject non-resident $FILE_NAME records too: the format requires\n$FILE_NAME to be resident and callers treat returned records as resident.","modified":"2026-08-18T03:56:38.870936239Z","published":"2026-08-15T05:54:04.772Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72209.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/d5803e3345dae9c6470bb61869885236276b9a35"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e4c36dfac57a7261e9aeb0f3a7f30944a8aefb56"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72209.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72209"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"6ceb4cc81ef3409ff79dcb959771f9110787397a"},{"fixed":"e4c36dfac57a7261e9aeb0f3a7f30944a8aefb56"},{"fixed":"d5803e3345dae9c6470bb61869885236276b9a35"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72209.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.1.0"},{"fixed":"7.1.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72209.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}]}