{"api_version":"1","generated_at":"2026-09-12T10:56:37+00:00","cve":"CVE-2026-89696","urls":{"html":"https://cve.report/CVE-2026-89696","api":"https://cve.report/api/cve/CVE-2026-89696.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89696","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89696"},"summary":{"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":"PUBLISHED","assigner":"Linux","published_at":"2026-09-11 20:19:56","updated_at":"2026-09-11 20:19:56"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/35f248bd40b47b229d4999581df45b97daadd977","name":"https://git.kernel.org/stable/c/35f248bd40b47b229d4999581df45b97daadd977","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/c59738a00aa51b16adc1b5ceb7c80877168efb4d","name":"https://git.kernel.org/stable/c/c59738a00aa51b16adc1b5ceb7c80877168efb4d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/bf4d338dc8625d70c7f2cb0657d66851a7ac9154","name":"https://git.kernel.org/stable/c/bf4d338dc8625d70c7f2cb0657d66851a7ac9154","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/311f7d926630940650447cbd1c932b076b40a6c4","name":"https://git.kernel.org/stable/c/311f7d926630940650447cbd1c932b076b40a6c4","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89696","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89696","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b9e8638e3d9ed8334f1f7071e081860aac37e83e 35f248bd40b47b229d4999581df45b97daadd977 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b9e8638e3d9ed8334f1f7071e081860aac37e83e 311f7d926630940650447cbd1c932b076b40a6c4 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b9e8638e3d9ed8334f1f7071e081860aac37e83e bf4d338dc8625d70c7f2cb0657d66851a7ac9154 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b9e8638e3d9ed8334f1f7071e081860aac37e83e c59738a00aa51b16adc1b5ceb7c80877168efb4d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.6","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.6 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.109 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.50 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.4 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/nfsd/nfs4proc.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"35f248bd40b47b229d4999581df45b97daadd977","status":"affected","version":"b9e8638e3d9ed8334f1f7071e081860aac37e83e","versionType":"git"},{"lessThan":"311f7d926630940650447cbd1c932b076b40a6c4","status":"affected","version":"b9e8638e3d9ed8334f1f7071e081860aac37e83e","versionType":"git"},{"lessThan":"bf4d338dc8625d70c7f2cb0657d66851a7ac9154","status":"affected","version":"b9e8638e3d9ed8334f1f7071e081860aac37e83e","versionType":"git"},{"lessThan":"c59738a00aa51b16adc1b5ceb7c80877168efb4d","status":"affected","version":"b9e8638e3d9ed8334f1f7071e081860aac37e83e","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/nfsd/nfs4proc.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.6"},{"lessThan":"5.6","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.109","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.50","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.4","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.109","versionStartIncluding":"5.6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.50","versionStartIncluding":"5.6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.4","versionStartIncluding":"5.6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"5.6","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"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."}],"providerMetadata":{"dateUpdated":"2026-09-11T19:46:15.030Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/35f248bd40b47b229d4999581df45b97daadd977"},{"url":"https://git.kernel.org/stable/c/311f7d926630940650447cbd1c932b076b40a6c4"},{"url":"https://git.kernel.org/stable/c/bf4d338dc8625d70c7f2cb0657d66851a7ac9154"},{"url":"https://git.kernel.org/stable/c/c59738a00aa51b16adc1b5ceb7c80877168efb4d"}],"title":"nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89696","datePublished":"2026-09-11T19:46:15.030Z","dateReserved":"2026-09-11T19:38:34.750Z","dateUpdated":"2026-09-11T19:46:15.030Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-11 20:19:56","lastModifiedDate":"2026-09-11 20:19:56","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89696","Ordinal":"1","Title":"nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL d","CVE":"CVE-2026-89696","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89696","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL d"}]}}}