CVE-2026-53368
HIGHf2fs: fix fsck inconsistency caused by incorrect nat_entry flag usage
Blast Radius
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Description
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix fsck inconsistency caused by incorrect nat_entry flag usage
f2fs_need_dentry_mark() reads nat_entry flags without mutual exclusion with the checkpoint path, which can result in an incorrect inode block marking state. The scenario is as follows:
create & write & fsync 'file A' write checkpoint
- f2fs_do_sync_file // inline inode
- f2fs_write_inode // inode folio is dirty - f2fs_write_checkpoint - f2fs_flush_merged_writes - f2fs_sync_node_pages
- f2fs_fsync_node_pages // no dirty node
- f2fs_need_inode_block_update // return true
- f2fs_fsync_node_pages // inode dirtied
- f2fs_need_dentry_mark //return true - f2fs_flush_nat_entries - f2fs_write_checkpoint end
- __write_node_folio // inode with DENT_BIT_SHIFT set SPO, "fsck --dry-run" find inode has already checkpointed but still with DENT_BIT_SHIFT set
The state observed by f2fs_need_dentry_mark() can differ from the state observed in __write_node_folio() after acquiring sbi->node_write. The root cause is that the semantics of IS_CHECKPOINTED and HAS_FSYNCED_INODE are only guaranteed after the checkpoint write has fully completed.
This patch moves set_dentry_mark() into __write_node_folio() and protects it with the sbi->node_write lock.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐧Linux | Kernel | ≥ 3.18.0&&< 6.18.30 | 6.18.30 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Kernel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update Kernel to 6.18.30 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53368 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-53368 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-53368. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-53368 in your dependencies?
O3 detects CVE-2026-53368 across Linux dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.