# CVE-2026-53320: nilfs2: reject zero bd_oblocknr in nilfs_ioctl_mark_blocks_dirty()

CVE-2026-53320 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-53320, released June 27, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-53320
- Priority: Routine
- CVSS: 5.5 (Moderate)
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 26, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-53320

## Description

In the Linux kernel, the following vulnerability has been resolved:  nilfs2: reject zero bd_oblocknr in nilfs_ioctl_mark_blocks_dirty()  nilfs_ioctl_mark_blocks_dirty() uses bd_oblocknr to detect dead blocks by comparing it with the current block number bd_blocknr. If they differ, the block is considered dead and skipped.  However, bd_oblocknr should never be 0 since block 0 typically stores the primary superblock and is never a valid GC target block. A corrupted ioctl request with bd_oblocknr set to 0 causes the comparison to incorrectly match when the lookup returns -ENOENT and sets bd_blocknr to 0, bypassing the dead block check and calling nilfs_bmap_mark() on a non-existent block. This causes nilfs_btree_do_lookup() to return -ENOENT, triggering the WARN_ON(ret == -ENOENT).  Fix this by rejecting ioctl requests with bd_oblocknr set to 0 at the beginning of each iteration.  [ryusuke: slightly modified the commit message and comments for accuracy]

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.176-1 | [DEBIAN-CVE-2026-53320](https://patchblox.com/security/data/fix/linux/debian-cve-2026-53320.md) | Jun 27, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.94-1 | [DEBIAN-CVE-2026-53320](https://patchblox.com/security/data/fix/linux/debian-cve-2026-53320.md) | Jun 27, 2026 |
| Linux | linux Debian 14 | 7.0.10-1 | [DEBIAN-CVE-2026-53320](https://patchblox.com/security/data/fix/linux/debian-cve-2026-53320.md) | Jun 27, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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