# CVE-2026-90418: nilfs2: fix BUG in nilfs_copy_dirty_pages() on dirty state mismatch

CVE-2026-90418 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-90418, released September 23, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-90418
- Priority: Routine
- CVSS: 5.5 (Moderate)
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 17, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-90418

## Description

In the Linux kernel, the following vulnerability has been resolved:  nilfs2: fix BUG in nilfs_copy_dirty_pages() on dirty state mismatch  Syzbot reported a kernel BUG triggered within nilfs_copy_dirty_pages(), which copies dirty DAT file folios/pages to its shadow page cache.  The BUG occurs when a retrieved dirty folio/page unexpectedly loses its 'dirty' status.  This issue arises because, since the commit referenced below, the 'dirty' flag of a folio/page can be cleared asynchronously after the filesystem detects metadata corruption and transitions to read-only mode.  Resolve the issue by returning an -EROFS error if the filesystem has transitioned to read-only mode.  Also change the behavior to issue a kernel warning only once instead of triggering a kernel BUG when this unexpected 'dirty' state is detected while the filesystem is not in read-only mode.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.111-1 | [DEBIAN-CVE-2026-90418](https://patchblox.com/security/data/fix/linux/debian-cve-2026-90418.md) | Sep 23, 2026 |
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-90418](https://patchblox.com/security/data/fix/linux/debian-cve-2026-90418.md) | Sep 23, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.111-1~deb12u1 | [DEBIAN-CVE-2026-90418](https://patchblox.com/security/data/fix/linux/debian-cve-2026-90418.md) | Sep 23, 2026 |

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Data as of 2026-11-09T01:18:40Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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