{"id":"CVE-2026-89640","state":"PUBLISHED","title":"cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: fix loff_t underflow in cifs_remap_file_range() when len == 0\n\nWith len == 0 (clone to EOF), the effective length is computed as:\n\n    len = src_inode->i_size - off;\n\nIf off > i_size, this is a negative loff_t, corrupting the ByteCount\nin the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range\nin filemap_write_and_wait_range().  The existing off >= i_size check\nfires only after the ioctl has already been sent.\n\nSnapshot i_size_read() once for both the bounds check and the length\ncalculation, eliminating the TOCTOU and 32-bit torn-read risk.  Reject\noff > src_size with -EINVAL.  Treat off == src_size as a no-op,\nconsistent with __generic_remap_file_range_prep().","publishedAt":"2026-09-11T19:45:33.289Z","updatedAt":"2026-10-30T12:32:24.876Z","severity":{"score":7.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"2c6eede83b3de1268db92c7e49741761c954aa26","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"ce813e5eebf46851e872ce59bdc34dc5dd4e29a4","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"7f62817fe049b0f3652518c1ba72631ec1e0a322","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"b098f5e5858797827666e6cd73033f52fc39b5f6","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"b057ca17b656345d04669cb87f2aff9b31d873db","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"6c322f5cf7476ded7a9a20f7be72462065a03c68","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/cifsfs.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.5","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.5","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.109","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/cifsfs.c"]}],"references":["https://git.kernel.org/stable/c/2c6eede83b3de1268db92c7e49741761c954aa26","https://git.kernel.org/stable/c/ce813e5eebf46851e872ce59bdc34dc5dd4e29a4","https://git.kernel.org/stable/c/f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4","https://git.kernel.org/stable/c/7f62817fe049b0f3652518c1ba72631ec1e0a322","https://git.kernel.org/stable/c/b098f5e5858797827666e6cd73033f52fc39b5f6","https://git.kernel.org/stable/c/c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028","https://git.kernel.org/stable/c/b057ca17b656345d04669cb87f2aff9b31d873db","https://git.kernel.org/stable/c/6c322f5cf7476ded7a9a20f7be72462065a03c68"],"weaknesses":[],"ingestedAt":"2026-10-30T12:50:04.827Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/89xxx/CVE-2026-89640.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89640","state":"PUBLISHED","datePublished":"2026-09-11T19:45:33.289Z","dateUpdated":"2026-10-30T12:32:24.876Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.740Z"},"containers":{"cna":{"title":"cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: fix loff_t underflow in cifs_remap_file_range() when len == 0\n\nWith len == 0 (clone to EOF), the effective length is computed as:\n\n    len = src_inode->i_size - off;\n\nIf off > i_size, this is a negative loff_t, corrupting the ByteCount\nin the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range\nin filemap_write_and_wait_range().  The existing off >= i_size check\nfires only after the ioctl has already been sent.\n\nSnapshot i_size_read() once for both the bounds check and the length\ncalculation, eliminating the TOCTOU and 32-bit torn-read risk.  Reject\noff > src_size with -EINVAL.  Treat off == src_size as a no-op,\nconsistent with __generic_remap_file_range_prep()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"2c6eede83b3de1268db92c7e49741761c954aa26","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"ce813e5eebf46851e872ce59bdc34dc5dd4e29a4","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"7f62817fe049b0f3652518c1ba72631ec1e0a322","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"b098f5e5858797827666e6cd73033f52fc39b5f6","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"b057ca17b656345d04669cb87f2aff9b31d873db","versionType":"git"},{"version":"04b38d601239b4d9be641b412cf4b7456a041c67","status":"affected","lessThan":"6c322f5cf7476ded7a9a20f7be72462065a03c68","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/cifsfs.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.5","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.5","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.109","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/cifsfs.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/2c6eede83b3de1268db92c7e49741761c954aa26"},{"url":"https://git.kernel.org/stable/c/ce813e5eebf46851e872ce59bdc34dc5dd4e29a4"},{"url":"https://git.kernel.org/stable/c/f3d1ae1e6bc4a9f559185b6e7bd2b6375ec2fdd4"},{"url":"https://git.kernel.org/stable/c/7f62817fe049b0f3652518c1ba72631ec1e0a322"},{"url":"https://git.kernel.org/stable/c/b098f5e5858797827666e6cd73033f52fc39b5f6"},{"url":"https://git.kernel.org/stable/c/c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028"},{"url":"https://git.kernel.org/stable/c/b057ca17b656345d04669cb87f2aff9b31d873db"},{"url":"https://git.kernel.org/stable/c/6c322f5cf7476ded7a9a20f7be72462065a03c68"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H","baseScore":7.1,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is in the CIFS client remap method, reached from the local FICLONERANGE/FICLONE ioctls through vfs_clone_file_range() on an already-mounted CIFS share, not from SMB packet parsing in ksmbd or the TCP stack.\nAC:L - An attacker fully controls src_offset and src_length and can set length to 0 with offset past i_size, so the loff_t underflow is deterministic and does not depend on a race or memory layout they cannot influence.\nPR:L - vfs_clone_file_range() only requires a regular source opened for read and a regular destination opened for write; any unprivileged user with those fds on a CIFS mount can issue FICLONERANGE without capabilities or init-namespace root.\nUI:N - The attacker opens their own CIFS files and issues the ioctl; no separate victim action such as mounting a share or opening a file is required once a typical enterprise/autofs CIFS mount exists.\nS:U - Impact stays inside the host kernel and the CIFS inode/page cache of the same OS security authority; this is not a VM, IOMMU, or sandbox boundary crossing.\nC:N - The underflow does not read attacker-inaccessible kernel or file data; it miscomputes a clone length and then truncates destination page cache and sends a bad FSCTL, with no out-of-bounds or UAF read primitive.\nI:H - Negative len wraps destend to a huge uoff_t so truncate_inode_pages_range() discards the destination file's page cache, including dirty folios not flushed in the inverted range, silently destroying buffered data, and the same value corrupts ByteCount in FSCTL_DUPLICATE_EXTENTS_TO_FILE.\nA:H - The same wrapped range and signed-to-u64 conversion can set a huge/negative EOF via smb2_set_file_size()/cifs_resize_file_locked() on duplicate-extents servers and leave netfs/pagecache state inconsistent, which can oops, hang, or deny access to the affected file and kernel paths."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:32:24.876Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.5","versionEndExcluding":"5.10.273"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.5","versionEndExcluding":"5.15.224"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.5","versionEndExcluding":"6.1.188"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.5","versionEndExcluding":"6.6.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.5","versionEndExcluding":"6.12.109"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.5","versionEndExcluding":"6.18.50"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.5","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.5","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-89640","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T19:24:54.678656Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T19:26:45.931Z"}}]}}}