{"api_version":"1","generated_at":"2026-08-28T19:29:27+00:00","cve":"CVE-2026-74321","urls":{"html":"https://cve.report/CVE-2026-74321","api":"https://cve.report/api/cve/CVE-2026-74321.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-74321","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-74321"},"summary":{"title":"btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()\n\nIn the beginning of the loop, we try to obtain a locked delayed ref head,\nif 'locked_ref' is currently NULL, by calling btrfs_select_ref_head(),\nwhich can return an error pointer. If the error pointer is -EAGAIN we do\na continue and go back to the beginning of the loop, which will not try\nagain to call btrfs_select_ref_head() since 'locked_ref' is no longer\nNULL but it's ERR_PTR(-EAGAIN), and then we do:\n\n   spin_lock(&locked_ref->lock);\n\nagainst a ERR_PTR(-EAGAIN) value, generating an invalid pointer\ndereference.\n\nFix this by ensuring that 'locked_ref' is set to NULL when\nbtrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing 'count'\nas well, to prevent infinite looping. We do this by doing a goto to the\nbottom of the loop that already sets 'locked_ref' to NULL and does a\ncond_resched(), with an increment to 'count' right before the goto.\nThese measures were in place before the refactoring in commit 0110a4c43451\n(\"btrfs: refactor __btrfs_run_delayed_refs loop\") but were unintentionally\nlost afterwards.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-08-15 06:22:32","updated_at":"2026-08-17 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Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74321","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 0110a4c43451533de1ea1bbdc57b5d452f9d8b25 c372ca227e16bace86f1df1fa4ae6849e2fcfa28 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 0110a4c43451533de1ea1bbdc57b5d452f9d8b25 a71143590ce9764dbcb47617647592ff8b4d48bc git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 0110a4c43451533de1ea1bbdc57b5d452f9d8b25 65770111a2d47c2b15e20b2ba92bb12198f289d4 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 0110a4c43451533de1ea1bbdc57b5d452f9d8b25 015dc4a1e0c2cba551d4620eba13d26d5081dc34 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"74321","cve":"CVE-2026-74321","epss":"0.005080000","percentile":"0.409950000","score_date":"2026-08-17","updated_at":"2026-08-18 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the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()\n\nIn the beginning of the loop, we try to obtain a locked delayed ref head,\nif 'locked_ref' is currently NULL, by calling btrfs_select_ref_head(),\nwhich can return an error pointer. If the error pointer is -EAGAIN we do\na continue and go back to the beginning of the loop, which will not try\nagain to call btrfs_select_ref_head() since 'locked_ref' is no longer\nNULL but it's ERR_PTR(-EAGAIN), and then we do:\n\n   spin_lock(&locked_ref->lock);\n\nagainst a ERR_PTR(-EAGAIN) value, generating an invalid pointer\ndereference.\n\nFix this by ensuring that 'locked_ref' is set to NULL when\nbtrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing 'count'\nas well, to prevent infinite looping. We do this by doing a goto to the\nbottom of the loop that already sets 'locked_ref' to NULL and does a\ncond_resched(), with an increment to 'count' right before the goto.\nThese measures were in place before the refactoring in commit 0110a4c43451\n(\"btrfs: refactor __btrfs_run_delayed_refs loop\") but were unintentionally\nlost afterwards."}],"metrics":[{"cvssV3_1":{"baseScore":7.5,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:N - On storage servers exporting btrfs via nfsd or ksmbd, remote client write/fsync/unlink I/O reaches btrfs_run_delayed_refs() and __btrfs_run_delayed_refs() in the server kernel without any local syscall; this is the highest-impact but reasonable deployment for btrfs metadata processing.\nAC:L - -EAGAIN is returned when a concurrent task deletes the delayed-ref head during btrfs_delayed_ref_lock(); an attacker controls both sides by driving parallel writes/unlinks/fsync or multiple NFS/SMB clients, reliably hitting the documented race without uncontrollable layout or victim state.\nPR:N - Exploitation needs only network write access to an NFS or SMB export of the btrfs filesystem; no local account, Linux capability, or init-namespace privilege is required when the export permits client writes (including anonymous/guest exports common on NAS appliances).\nUI:N - The fault is triggered entirely by the attacker's own concurrent filesystem I/O against an already-exported btrfs volume; no separate victim must mount a filesystem, open a file, or perform any interactive action beyond the attacker's own operations.\nS:U - The invalid pointer dereference and resulting kernel oops occur within the host kernel's btrfs delayed-ref processing; no VM escape, IOMMU bypass, or cross-sandbox boundary is crossed.\nC:N - The bug dereferences ERR_PTR(-EAGAIN), a small negative sentinel address, not freed or attacker-controlled memory; spin_lock faults immediately without returning kernel data, so there is no information-disclosure or read primitive.\nI:N - This is a logic error causing an invalid pointer dereference, not a use-after-free, out-of-bounds write, or type confusion; no kernel memory is modified before the faulting access aborts execution.\nA:H - Dereferencing ERR_PTR(-EAGAIN) in spin_lock(&locked_ref->lock) causes a kernel oops/panic during delayed-ref processing, which can hang or crash the host and deny all service on the affected btrfs filesystem; the condition is repeatable with concurrent I/O."}]}],"providerMetadata":{"dateUpdated":"2026-08-17T05:45:52.396Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/c372ca227e16bace86f1df1fa4ae6849e2fcfa28"},{"url":"https://git.kernel.org/stable/c/a71143590ce9764dbcb47617647592ff8b4d48bc"},{"url":"https://git.kernel.org/stable/c/65770111a2d47c2b15e20b2ba92bb12198f289d4"},{"url":"https://git.kernel.org/stable/c/015dc4a1e0c2cba551d4620eba13d26d5081dc34"},{"url":"https://git.kernel.org/stable/c/ba9fa2ff5981589bb49094d3358c339b37c47f53"},{"url":"https://git.kernel.org/stable/c/3b15d02be05e74321adb1e0ae0cb4ccfba7c6cb1"},{"url":"https://git.kernel.org/stable/c/9faa6b69ad73f03c7bde53e07d75a28822dc9a1a"},{"url":"https://git.kernel.org/stable/c/486f8298b6188ff11ef1f4be7f1d5d2e4d1b1fae"}],"title":"btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-74321","datePublished":"2026-08-15T05:58:17.485Z","dateReserved":"2026-08-15T05:44:03.884Z","dateUpdated":"2026-08-17T05:45:52.396Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-15 06:22:32","lastModifiedDate":"2026-08-17 06:19:26","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"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","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":3.6}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"74321","Ordinal":"1","Title":"btrfs: fix invalid pointer dereference in __btrfs_run_delayed_re","CVE":"CVE-2026-74321","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"74321","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()\n\nIn the beginning of the loop, we try to obtain a locked delayed ref head,\nif 'locked_ref' is currently NULL, by calling btrfs_select_ref_head(),\nwhich can return an error pointer. If the error pointer is -EAGAIN we do\na continue and go back to the beginning of the loop, which will not try\nagain to call btrfs_select_ref_head() since 'locked_ref' is no longer\nNULL but it's ERR_PTR(-EAGAIN), and then we do:\n\n   spin_lock(&locked_ref->lock);\n\nagainst a ERR_PTR(-EAGAIN) value, generating an invalid pointer\ndereference.\n\nFix this by ensuring that 'locked_ref' is set to NULL when\nbtrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing 'count'\nas well, to prevent infinite looping. We do this by doing a goto to the\nbottom of the loop that already sets 'locked_ref' to NULL and does a\ncond_resched(), with an increment to 'count' right before the goto.\nThese measures were in place before the refactoring in commit 0110a4c43451\n(\"btrfs: refactor __btrfs_run_delayed_refs loop\") but were unintentionally\nlost afterwards.","Type":"Description","Title":"btrfs: fix invalid pointer dereference in __btrfs_run_delayed_re"}]}}}