{"id":"CVE-2026-89678","revision":"28f26e081caa4ea080e90052b881a4b4","records":[{"revision":"28f26e081caa4ea080e90052b881a4b4","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-89678","aliases":[],"title":"nfsd: fix partial-write detection in nfsd_direct_write","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix partial-write detection in nfsd_direct_write\n\nnfsd_direct_write() walks a list of write segments and, after each\nvfs_iocb_iter_write(), tries to detect a short write so the loop can\nstop before placing the next segment at a wrong file offset:\n\n    host_err = vfs_iocb_iter_write(file, kiocb, &segments[i].iter);\n    if (host_err < 0)\n            return host_err;\n    *cnt += host_err;\n    if (host_err < segments[i].iter.count)\n            break;\t/* partial write */\n\nvfs_iocb_iter_write() runs the iter through ->write_iter(), which\nadvances the iter by the number of bytes written. By the time the\ncheck runs, segments[i].iter.count is the residual, not the original\nrequest length:\n\n    before write_iter: iter.count == original_len\n    after  write_iter: iter.count == original_len - host_err\n\nThe condition then reduces to host_err < original_len - host_err, so\nthe break fires only when less than half of the segment was written.\nAny short write completing between 50% and 99% of the segment slips\nthrough; the loop advances to the next segment with kiocb->ki_pos\nonly bumped by the short amount, writing the next segment's payload\nat the wrong offset and over-reporting *cnt to the NFS client.\n\nSnapshot the segment's byte count before the write and compare\nhost_err against that snapshot so any short write breaks the loop.","state":0,"publishedAt":"2026-09-11T19:46:02.184+00:00","modifiedAt":"2026-10-19T08:50:51.587+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/nfsd/vfs.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"06c5c97293e3fca99ce15da157068edf45a7c6e4\",\n                            \"lessThan\": \"fa6590dfd16ab55f03b658b079072ace3504825e\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"06c5c97293e3fca99ce15da157068edf45a7c6e4\",\n                            \"lessThan\": \"250ec14932d5cfe102f68a57892bb566eee7f83e\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/nfsd/vfs.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.19\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"6.19\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.4\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","score":7.5,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/fa6590dfd16ab55f03b658b079072ace3504825e","https://git.kernel.org/stable/c/250ec14932d5cfe102f68a57892bb566eee7f83e"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89678","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-89678","identifiers":["CVE-2026-89678"]},"retained":false,"historicalAffected":[]}],"coverage":[]}