{"api_version":"1","generated_at":"2026-10-27T04:25:06+00:00","cve":"CVE-2026-98543","urls":{"html":"https://cve.report/CVE-2026-98543","api":"https://cve.report/api/cve/CVE-2026-98543.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98543","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98543"},"summary":{"title":"bpf: fs/xattr: don't assume the inode is locked in path_unlink/path_rmdir","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: fs/xattr: don't assume the inode is locked in path_unlink/path_rmdir\n\nbpf_lsm_has_d_inode_locked() makes the verifier rewrite\nbpf_[set|remove]_dentry_xattr() to the _locked variants, which assume\nthat the caller already holds the inode's i_rwsem.  The path_unlink and\npath_rmdir hooks are listed, but security_path_unlink() and\nsecurity_path_rmdir() run before vfs_unlink()/vfs_rmdir() take the\nvictim inode's i_rwsem, so a sleepable BPF LSM program attached to\neither hook mutates the victim's xattrs without the lock held.\n\nDrop the two path hooks from d_inode_locked_hooks so that the verifier\nkeeps the locking bpf_[set|remove]_dentry_xattr() variants, which take\nthe lock themselves.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-10-18 16:17:06","updated_at":"2026-10-24 14:16:46"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"7.3","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H","baseScore":7.3,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"NONE","integrityImpact":"LOW","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"7.3","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H","data":{"baseScore":7.3,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/640d37fbd34d03af727dbc567f48c0203d1de6b4","name":"https://git.kernel.org/stable/c/640d37fbd34d03af727dbc567f48c0203d1de6b4","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/7504b677c4370c9e4b153c553ff8831c093b1ff6","name":"https://git.kernel.org/stable/c/7504b677c4370c9e4b153c553ff8831c093b1ff6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/35d442ed1f86465e49df3119fb898f985186db13","name":"https://git.kernel.org/stable/c/35d442ed1f86465e49df3119fb898f985186db13","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98543","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98543","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 56467292794b800164df20c076c409ac548e56ec 7504b677c4370c9e4b153c553ff8831c093b1ff6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 56467292794b800164df20c076c409ac548e56ec 640d37fbd34d03af727dbc567f48c0203d1de6b4 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 56467292794b800164df20c076c409ac548e56ec 35d442ed1f86465e49df3119fb898f985186db13 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.15","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.15 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.55 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.9 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3 * 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/bpf_fs_kfuncs.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"7504b677c4370c9e4b153c553ff8831c093b1ff6","status":"affected","version":"56467292794b800164df20c076c409ac548e56ec","versionType":"git"},{"lessThan":"640d37fbd34d03af727dbc567f48c0203d1de6b4","status":"affected","version":"56467292794b800164df20c076c409ac548e56ec","versionType":"git"},{"lessThan":"35d442ed1f86465e49df3119fb898f985186db13","status":"affected","version":"56467292794b800164df20c076c409ac548e56ec","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/bpf_fs_kfuncs.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.15"},{"lessThan":"6.15","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.55","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.9","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.55","versionStartIncluding":"6.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.9","versionStartIncluding":"6.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3","versionStartIncluding":"6.15","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: fs/xattr: don't assume the inode is locked in path_unlink/path_rmdir\n\nbpf_lsm_has_d_inode_locked() makes the verifier rewrite\nbpf_[set|remove]_dentry_xattr() to the _locked variants, which assume\nthat the caller already holds the inode's i_rwsem.  The path_unlink and\npath_rmdir hooks are listed, but security_path_unlink() and\nsecurity_path_rmdir() run before vfs_unlink()/vfs_rmdir() take the\nvictim inode's i_rwsem, so a sleepable BPF LSM program attached to\neither hook mutates the victim's xattrs without the lock held.\n\nDrop the two path hooks from d_inode_locked_hooks so that the verifier\nkeeps the locking bpf_[set|remove]_dentry_xattr() variants, which take\nthe lock themselves."}],"metrics":[{"cvssV3_1":{"baseScore":7.3,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:L - unlink(2)/unlinkat(2)/rmdir(2) reach filename_unlinkat()/filename_rmdir() -> security_path_unlink()/security_path_rmdir() -> bpf_lsm_path_*(); vulnerable bpf_lsm_has_d_inode_locked() classification makes the verifier redirect bpf_[set|remove]_dentry_xattr() to _locked functions. The trigger enters locally, not via a protocol.\nAC:L - On UBIFS, one invocation deterministically fails ubifs_xattr_set()/ubifs_xattr_remove()'s inode_is_locked() assertion; for races, the attacker can unlink two hardlinks in different parents concurrently, so separate parent locks do not serialize the same victim. No condition is outside the attacker's control.\nPR:L - bpf_prog_load() gates BPF_PROG_TYPE_LSM on bpf_token_capable(CAP_BPF) and CAP_PERFMON. A delegated bpffs token makes those ns_capable(token->userns, ...) checks, so a namespace-confined non-admin can load and attach the sleepable path hook; without delegation, init-namespace capabilities are required.\nUI:N - The attacker loads and attaches the BPF LSM program, then invokes unlinkat(2) or rmdir(2) on an object it can modify; no victim must mount media, open a file, or perform another action.\nS:C - With bpffs token delegation, a task confined to the token's user namespace can run the faulty BPF LSM program in the host kernel and force a shared host UBIFS read-only, crossing the container or sandbox availability boundary.\nC:N - Neither affected helper returns filesystem or kernel data: bpf_set_dentry_xattr_locked() only passes a verifier-bounded dynptr to __vfs_setxattr(), and the remove helper has no output. The missing i_rwsem is a mutation-ordering flaw, with no demonstrated OOB read, UAF, or disclosure path.\nI:L - btrfs_setxattr() explicitly relies on the inode lock to exclude a concurrent delete between its XATTR_REPLACE lookup and insert; this bug removes that exclusion, so concurrent path_unlink hooks can recreate or lose security.bpf.* metadata. Btrfs tree locking shows no arbitrary-memory-write primitive, limiting integrity impact.\nA:H - ubifs_xattr_set(..., check_lock=true) and ubifs_xattr_remove() assert inode_is_locked(); default ASSACT_RO calls ubifs_ro_mode(), sets SB_RDONLY, and denies later writes. One path hook calling the mis-selected _locked helper can therefore make a mounted UBIFS lose write availability."}]}],"providerMetadata":{"dateUpdated":"2026-10-24T14:09:20.159Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/7504b677c4370c9e4b153c553ff8831c093b1ff6"},{"url":"https://git.kernel.org/stable/c/640d37fbd34d03af727dbc567f48c0203d1de6b4"},{"url":"https://git.kernel.org/stable/c/35d442ed1f86465e49df3119fb898f985186db13"}],"title":"bpf: fs/xattr: don't assume the inode is locked in path_unlink/path_rmdir","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98543","datePublished":"2026-10-18T15:18:10.823Z","dateReserved":"2026-09-25T10:25:14.356Z","dateUpdated":"2026-10-24T14:09:20.159Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-18 16:17:06","lastModifiedDate":"2026-10-24 14:16:46","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H","baseScore":7.3,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"NONE","integrityImpact":"LOW","availabilityImpact":"HIGH"},"exploitabilityScore":2,"impactScore":4.7}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98543","Ordinal":"1","Title":"bpf: fs/xattr: don't assume the inode is locked in path_unlink/p","CVE":"CVE-2026-98543","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98543","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: fs/xattr: don't assume the inode is locked in path_unlink/path_rmdir\n\nbpf_lsm_has_d_inode_locked() makes the verifier rewrite\nbpf_[set|remove]_dentry_xattr() to the _locked variants, which assume\nthat the caller already holds the inode's i_rwsem.  The path_unlink and\npath_rmdir hooks are listed, but security_path_unlink() and\nsecurity_path_rmdir() run before vfs_unlink()/vfs_rmdir() take the\nvictim inode's i_rwsem, so a sleepable BPF LSM program attached to\neither hook mutates the victim's xattrs without the lock held.\n\nDrop the two path hooks from d_inode_locked_hooks so that the verifier\nkeeps the locking bpf_[set|remove]_dentry_xattr() variants, which take\nthe lock themselves.","Type":"Description","Title":"bpf: fs/xattr: don't assume the inode is locked in path_unlink/p"}]}}}