{"id":"CVE-2026-89696","revision":"81dc1911a96049ceb6f0766e4124a112","records":[{"revision":"81dc1911a96049ceb6f0766e4124a112","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-89696","aliases":[],"title":"nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref\n\nWhen CONFIG_NFSD_V4_2_INTER_SSC is enabled, nfsd4_putfh() can return\nsuccess with fh_dentry and fh_export both NULL if fh_verify() returns\nnfserr_stale and putfh->no_verify is true. The NFSD4_FH_FOREIGN flag\nis set, but the compound dispatch loop only uses this flag to bypass\nthe nfserr_nofilehandle check -- it does not prevent subsequent ops\nfrom running with a NULL fh_dentry.\n\nA remote client can exploit this by crafting a COMPOUND that includes\nan inter-SSC COPY (which causes check_if_stalefh_allowed() to set\nno_verify=true on the saved PUTFH) with an additional op inserted\nbetween the source PUTFH and SAVEFH. For example, SETATTR calls\nfh_want_write() which dereferences fh_export->ex_path.mnt without\ncalling fh_verify() first, causing a NULL pointer dereference in the\nnfsd kthread.\n\nFix this by gating the dispatch loop: when NFSD4_FH_FOREIGN is set\nand fh_dentry is NULL, only OP_SAVEFH (needed for the inter-SSC flow)\nand ops with ALLOWED_WITHOUT_FH (which don't need a resolved\nfilehandle) may proceed. All other ops receive nfserr_stale, per\nRFC 7862 Section 15.2.3 which specifies that foreign filehandle\nvalidation is deferred to the consuming operation and NFS4ERR_STALE\nreturned at that point.","state":0,"publishedAt":"2026-09-11T19:46:15.03+00:00","modifiedAt":"2026-10-19T08:51:09.479+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/nfs4proc.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"b9e8638e3d9ed8334f1f7071e081860aac37e83e\",\n                            \"lessThan\": \"ffdc844e673d2bcb2af8c8c3eef8cdea59d0bf32\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b9e8638e3d9ed8334f1f7071e081860aac37e83e\",\n                            \"lessThan\": \"00c84f4eec715e501efc080a5670114189e42507\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b9e8638e3d9ed8334f1f7071e081860aac37e83e\",\n                            \"lessThan\": \"2d9846fd1c767920fddd4bde30eb35cd2969df13\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b9e8638e3d9ed8334f1f7071e081860aac37e83e\",\n                            \"lessThan\": \"977e6f006a7a3ffc4216ae6034f768f8de6fd138\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b9e8638e3d9ed8334f1f7071e081860aac37e83e\",\n                            \"lessThan\": \"35f248bd40b47b229d4999581df45b97daadd977\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b9e8638e3d9ed8334f1f7071e081860aac37e83e\",\n                            \"lessThan\": \"311f7d926630940650447cbd1c932b076b40a6c4\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b9e8638e3d9ed8334f1f7071e081860aac37e83e\",\n                            \"lessThan\": \"bf4d338dc8625d70c7f2cb0657d66851a7ac9154\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b9e8638e3d9ed8334f1f7071e081860aac37e83e\",\n                            \"lessThan\": \"c59738a00aa51b16adc1b5ceb7c80877168efb4d\",\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/nfs4proc.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"5.6\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"5.6\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.270\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.221\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.188\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.157\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.109\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.50\",\n                            \"lessThanOrEqual\": \"6.18.*\",\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:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/ffdc844e673d2bcb2af8c8c3eef8cdea59d0bf32","https://git.kernel.org/stable/c/00c84f4eec715e501efc080a5670114189e42507","https://git.kernel.org/stable/c/2d9846fd1c767920fddd4bde30eb35cd2969df13","https://git.kernel.org/stable/c/977e6f006a7a3ffc4216ae6034f768f8de6fd138","https://git.kernel.org/stable/c/35f248bd40b47b229d4999581df45b97daadd977","https://git.kernel.org/stable/c/311f7d926630940650447cbd1c932b076b40a6c4","https://git.kernel.org/stable/c/bf4d338dc8625d70c7f2cb0657d66851a7ac9154","https://git.kernel.org/stable/c/c59738a00aa51b16adc1b5ceb7c80877168efb4d"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89696","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-89696","identifiers":["CVE-2026-89696"]},"retained":false,"historicalAffected":[]}],"coverage":[]}