{"id":"CVE-2026-74321","state":"PUBLISHED","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.","publishedAt":"2026-08-15T05:58:17.485Z","updatedAt":"2026-10-16T18:55:32.917Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"c372ca227e16bace86f1df1fa4ae6849e2fcfa28","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"a71143590ce9764dbcb47617647592ff8b4d48bc","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"65770111a2d47c2b15e20b2ba92bb12198f289d4","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"015dc4a1e0c2cba551d4620eba13d26d5081dc34","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"ba9fa2ff5981589bb49094d3358c339b37c47f53","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"3b15d02be05e74321adb1e0ae0cb4ccfba7c6cb1","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"9faa6b69ad73f03c7bde53e07d75a28822dc9a1a","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"486f8298b6188ff11ef1f4be7f1d5d2e4d1b1fae","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/extent-tree.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.20","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.20","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/extent-tree.c"]}],"references":["https://git.kernel.org/stable/c/c372ca227e16bace86f1df1fa4ae6849e2fcfa28","https://git.kernel.org/stable/c/a71143590ce9764dbcb47617647592ff8b4d48bc","https://git.kernel.org/stable/c/65770111a2d47c2b15e20b2ba92bb12198f289d4","https://git.kernel.org/stable/c/015dc4a1e0c2cba551d4620eba13d26d5081dc34","https://git.kernel.org/stable/c/ba9fa2ff5981589bb49094d3358c339b37c47f53","https://git.kernel.org/stable/c/3b15d02be05e74321adb1e0ae0cb4ccfba7c6cb1","https://git.kernel.org/stable/c/9faa6b69ad73f03c7bde53e07d75a28822dc9a1a","https://git.kernel.org/stable/c/486f8298b6188ff11ef1f4be7f1d5d2e4d1b1fae"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74321.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74321","state":"PUBLISHED","datePublished":"2026-08-15T05:58:17.485Z","dateUpdated":"2026-10-16T18:55:32.917Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.884Z"},"containers":{"cna":{"title":"btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"c372ca227e16bace86f1df1fa4ae6849e2fcfa28","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"a71143590ce9764dbcb47617647592ff8b4d48bc","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"65770111a2d47c2b15e20b2ba92bb12198f289d4","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"015dc4a1e0c2cba551d4620eba13d26d5081dc34","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"ba9fa2ff5981589bb49094d3358c339b37c47f53","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"3b15d02be05e74321adb1e0ae0cb4ccfba7c6cb1","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"9faa6b69ad73f03c7bde53e07d75a28822dc9a1a","versionType":"git"},{"version":"0110a4c43451533de1ea1bbdc57b5d452f9d8b25","status":"affected","lessThan":"486f8298b6188ff11ef1f4be7f1d5d2e4d1b1fae","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/extent-tree.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.20","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.20","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/extent-tree.c"]}],"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"}],"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 - 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":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T05:45:52.396Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"5.10.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-74321","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T18:53:22.742693Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T18:55:32.917Z"}}]}}}