{"id":"CVE-2026-52944","title":"ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE\n\nFSCTL_SET_SPARSE in fsctl_set_sparse() modifies the file's sparse\nattribute and sa…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < ef664475c1bf1a27d45dae6848ca9c9c4d86853f","Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < 3a9a0a1c38ef90788f5d7c4b29903c8b220f744a","Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < 3127a884525dc8ca4def73254bfcd3ccef0bf812","Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < c5ab11263e3c89aa7989afc5374ef7743e092fd0","Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < de9eb0b44fa9123170e6245b49638e0e453c10f8","Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < aef151bcfa494bfe983669de2726734b534adb73","Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < cc57232cae23c0df91b4a59d0f519141ce9b5b02","Linux 5.15"],"published":"2026-06-24","updated":"2026-09-14","sourceUpdated":"2026-09-14T11:58:26.890Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-52944","references":[{"url":"https://git.kernel.org/stable/c/ef664475c1bf1a27d45dae6848ca9c9c4d86853f"},{"url":"https://git.kernel.org/stable/c/3a9a0a1c38ef90788f5d7c4b29903c8b220f744a"},{"url":"https://git.kernel.org/stable/c/3127a884525dc8ca4def73254bfcd3ccef0bf812"},{"url":"https://git.kernel.org/stable/c/c5ab11263e3c89aa7989afc5374ef7743e092fd0"},{"url":"https://git.kernel.org/stable/c/de9eb0b44fa9123170e6245b49638e0e453c10f8"},{"url":"https://git.kernel.org/stable/c/aef151bcfa494bfe983669de2726734b534adb73"},{"url":"https://git.kernel.org/stable/c/cc57232cae23c0df91b4a59d0f519141ce9b5b02"}],"tags":["cve.org"],"epss":0.00122,"epssPercentile":0.02255,"ingestedAt":"2026-09-14T15:23:07.457Z","slug":"CVE-2026-52944","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE\n\nFSCTL_SET_SPARSE in fsctl_set_sparse() modifies the file's sparse\nattribute and saves it through xattr without any permission checks.\n\nThis exposes two issues:\n\n1) A client on a read-only share can change the sparse attribute\n   on files it opened, even though the share is read-only.\n   Other FSCTL write operations already check\n   test_tree_conn_flag(work->tcon, KSMBD_TREE_CONN_FLAG_WRITABLE),\n   but FSCTL_SET_SPARSE does not.\n\n2) Even on writable shares, clients without FILE_WRITE_DATA or\n   FILE_WRITE_ATTRIBUTES access should not modify the sparse\n   attribute. Similar handle-level checks exist in other functions\n   but are missing here.\n\nAdd both share-level writable check and per-handle access check.\nUse goto out on error to avoid leaking file references.\n\n## Affected\n\n- `Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < ef664475c1bf1a27d45dae6848ca9c9c4d86853f`\n- `Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < 3a9a0a1c38ef90788f5d7c4b29903c8b220f744a`\n- `Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < 3127a884525dc8ca4def73254bfcd3ccef0bf812`\n- `Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < c5ab11263e3c89aa7989afc5374ef7743e092fd0`\n- `Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < de9eb0b44fa9123170e6245b49638e0e453c10f8`\n- `Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < aef151bcfa494bfe983669de2726734b534adb73`\n- `Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < cc57232cae23c0df91b4a59d0f519141ce9b5b02`\n- `Linux 5.15`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}