{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89707", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.751Z", "datePublished": "2026-09-11T19:46:23.293Z", "dateUpdated": "2026-10-19T08:51:20.289Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:51:20.289Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: release path refs on follow_down() error\n\nnfsd_cross_mnt() initializes a local struct path with mntget() and\ndget() before calling follow_down(). On a negative return the error\narm jumps to out without releasing those references:\n\n err = follow_down(&path, follow_flags);\n if (err < 0)\n goto out;\n\nfollow_down() never drops the caller's entry-time refs on any error\nsub-case; for example a pre-cross d_manage() failure leaves path\nuntouched, so the mntget()/dget() taken on entry survive the call.\n\nEvery other early-exit arm in nfsd_cross_mnt() (other-namespace\nreturn, IS_ERR(exp2), and the success tail after the swap) already\ncalls path_put(&path); the err < 0 arm is the lone omission. The\nleak inflates mnt_count and d_count on each failed cross-mount,\nblocking umount and pinning dentries against the shrinker, and is\nreachable by any authenticated NFS client through nfsd_lookup_dentry\nor the NFSv4 READDIR encode path.\n\nFix by calling path_put(&path) before the goto out in the err < 0\narm so the entry-time refs are released on all follow_down() error\nreturns." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - nfsd_cross_mnt() runs in the in-kernel NFS server on TCP/UDP 2049 from nfsd_lookup_dentry() (NFSv2/v3/v4 LOOKUP) and nfsd4_encode_entry4_fattr() (NFSv4 READDIR); a remote client reaches it with ordinary RPC requests.\nAC:L - On a typical nfsd export of autofs homes or nested mounts with crossmnt, an attacker can deterministically make follow_down() fail (autofs d_manage/automount error) by repeating LOOKUP/READDIR of failing mount triggers; no race or victim-controlled layout is required.\nPR:N - Default nfsd exports accept RPC_AUTH_NULL and RPC_AUTH_UNIX with no password; fh_verify only checks export IP policy, a MOUNT/PUTROOTFH filehandle, and directory execute, so no Linux account or capability on the server is required.\nUI:N - The attacker triggers the leak with their own NFS LOOKUP or READDIR RPCs; no victim mount, click, or other interactive action is required.\nS:U - The leak inflates dentry and vfsmount refcounts inside the nfsd host kernel and does not cross a VM, IOMMU, or other separate security authority.\nC:N - The bug only fails to path_put() the mntget/dget taken before follow_down(); it does not read kernel or file data or provide an information-disclosure primitive.\nI:N - The bug does not write attacker-controlled data or corrupt kernel objects; it only retains extra references on existing dentries and mounts.\nA:H - Each failed follow_down() permanently pins the dentry and vfsmount; repeated LOOKUPs of distinct autofs/mountpoint names leave unreclaimable dentries, block umount, and can exhaust kernel memory for a system-wide DoS." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfsd/vfs.c" ], "versions": [ { "version": "cc53ce53c86924bfe98a12ea20b7465038a08792", "lessThan": "085cfde7c2186acaad103f02d2c25435ad5224e9", "status": "affected", "versionType": "git" }, { "version": "cc53ce53c86924bfe98a12ea20b7465038a08792", "lessThan": "194316df81263519156ebe714c4a286bee00e5be", "status": "affected", "versionType": "git" }, { "version": "cc53ce53c86924bfe98a12ea20b7465038a08792", "lessThan": "467d56fd3ff57447a790c6dc3ede2d02a947d224", "status": "affected", "versionType": "git" }, { "version": "cc53ce53c86924bfe98a12ea20b7465038a08792", "lessThan": "2bc4343308d85ee4e0dd3877b384306c96f114c2", "status": "affected", "versionType": "git" }, { "version": "cc53ce53c86924bfe98a12ea20b7465038a08792", "lessThan": "6cba08dc1922140d260cfeb30bbda4ee1bf869d8", "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/vfs.c" ], "versions": [ { "version": "2.6.38", "status": "affected" }, { "version": "0", "lessThan": "2.6.38", "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": "2.6.38", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.38", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.38", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.38", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.38", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/085cfde7c2186acaad103f02d2c25435ad5224e9" }, { "url": "https://git.kernel.org/stable/c/194316df81263519156ebe714c4a286bee00e5be" }, { "url": "https://git.kernel.org/stable/c/467d56fd3ff57447a790c6dc3ede2d02a947d224" }, { "url": "https://git.kernel.org/stable/c/2bc4343308d85ee4e0dd3877b384306c96f114c2" }, { "url": "https://git.kernel.org/stable/c/6cba08dc1922140d260cfeb30bbda4ee1bf869d8" } ], "title": "nfsd: release path refs on follow_down() error", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-89707", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:26:16.926763Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:49.252Z" } } ] } }