{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89711", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.751Z", "datePublished": "2026-09-11T19:46:26.269Z", "dateUpdated": "2026-10-19T08:51:24.221Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:51:24.221Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check\n\nThe header for commit e75b23f9e323 (\"nfsd: check d_can_lookup in\nfh_verify of directories\") details the assumption that justified\nadding the WARN_ON_ONCE to nfsd_mode_check(), that assumption is\ninvalid (in the case of NFS reexport).\n\nWhen NFSD exports an NFS filesystem it is very possible for\nnfsd_mode_check() to encounter a @dentry that doesn't have\ni_op->lookup (see nfs_fhget()'s NFS_ATTR_FATTR_MOUNTPOINT and\nNFS_ATTR_FATTR_V4_REFERRAL handling, and d_flags_for_inode()).\n\nSo remove nfsd_mode_check()'s WARN_ON_ONCE(). The nfserr_notdir\nreturn on that branch must stay. It guards the subsequent\nlookup_one_unlocked() -> __lookup_slow() path, which calls\ninode->i_op->lookup() with no NULL check, so returning nfserr_notdir\nis what keeps a client LOOKUP into such a @dentry from dereferencing\na NULL method pointer." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H", "baseScore": 8.2, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - nfsd is the in-kernel NFS server. A remote client reaches nfsd_mode_check() via directory ops (LOOKUP, CREATE, OPEN) over TCP/UDP 2049: svc_recv to nfsd_dispatch to fh_verify to __fh_verify.\nAC:L - On an nfsd host that reexports NFS, mountpoint and NFSv4 referral dentries lack i_op->lookup so d_can_lookup() is false. A client LOOKUP or other S_IFDIR fh_verify on that filehandle hits WARN_ON_ONCE deterministically with no race.\nPR:N - nfsd_mode_check() runs in __fh_verify() after filehandle decode but before check_security_flavor() and nfsd_permission(). Typical nfsd deployments accept AUTH_SYS/AUTH_NULL, so an unauthenticated peer that can reach the export triggers it with self-asserted credentials.\nUI:N - The attacker sends the NFS RPCs (NFSv4 PUTFH plus LOOKUP, or NFSv3 LOOKUP) themselves. No victim user must mount a filesystem, open a file, or otherwise interact.\nS:U - The WARN_ON_ONCE splat and any panic_on_warn crash remain inside the NFS server kernel. This is not a VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:L - WARN_ON_ONCE calls __warn()/dump_stack(), disclosing kernel text addresses in dmesg. There is no use-after-free or out-of-bounds read; the path returns nfserr_notdir without copying kernel memory to the client.\nI:N - The fix only removes the warning. The existing nfserr_notdir return already blocks lookup_one_unlocked() from calling a NULL i_op->lookup, so there is no memory corruption, write primitive, or control-flow hijack.\nA:H - WARN_ON_ONCE taints the kernel and panics the host when panic_on_warn is enabled or warn_limit is exceeded, so a remote NFS client can deny service by operating on a reexported mountpoint or referral directory." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfsfh.c" ], "versions": [ { "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c", "lessThan": "ae251937c6f0237e5b555a5e4ba4595b8206e865", "status": "affected", "versionType": "git" }, { "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c", "lessThan": "e145e8d67a5d41c72d322e7f87ab474d39d9dfb7", "status": "affected", "versionType": "git" }, { "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c", "lessThan": "9f4434893a2783f7384d993cea883aff3fb7a52d", "status": "affected", "versionType": "git" }, { "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c", "lessThan": "2ef131323999539038e306773c8256403834361b", "status": "affected", "versionType": "git" }, { "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c", "lessThan": "b55b4d880bb080fa10eb08ba21a5d8679b8102fe", "status": "affected", "versionType": "git" }, { "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c", "lessThan": "7ef182a8fe9c12b0d936880b1e504840639aa009", "status": "affected", "versionType": "git" }, { "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c", "lessThan": "a275de3bac5635514ca830f2e46b5ff0e66b5c4c", "status": "affected", "versionType": "git" }, { "version": "e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c", "lessThan": "aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/nfsfh.c" ], "versions": [ { "version": "4.8", "status": "affected" }, { "version": "0", "lessThan": "4.8", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.270", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.221", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.188", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.157", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.109", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.10.270" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.15.221" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.1.188" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/ae251937c6f0237e5b555a5e4ba4595b8206e865" }, { "url": "https://git.kernel.org/stable/c/e145e8d67a5d41c72d322e7f87ab474d39d9dfb7" }, { "url": "https://git.kernel.org/stable/c/9f4434893a2783f7384d993cea883aff3fb7a52d" }, { "url": "https://git.kernel.org/stable/c/2ef131323999539038e306773c8256403834361b" }, { "url": "https://git.kernel.org/stable/c/b55b4d880bb080fa10eb08ba21a5d8679b8102fe" }, { "url": "https://git.kernel.org/stable/c/7ef182a8fe9c12b0d936880b1e504840639aa009" }, { "url": "https://git.kernel.org/stable/c/a275de3bac5635514ca830f2e46b5ff0e66b5c4c" }, { "url": "https://git.kernel.org/stable/c/aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e" } ], "title": "NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-89711", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:26:26.232461Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:36:59.484Z" } } ] } }