# CVE-2026-80807: nilfs2: reject invalid block index in GC ioctl

CVE-2026-80807 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-80807, released September 5, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-80807
- Priority: Routine
- CVSS: 6.0 (Moderate)
- EPSS: 0.0020
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 4, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-80807

## Description

In the Linux kernel, the following vulnerability has been resolved:  nilfs2: reject invalid block index in GC ioctl  Syzbot reported list corruption caused by a double list_add_tail() call on bh->b_assoc_buffers within nilfs_lookup_dirty_data_buffers().  Analysis revealed that the root cause was the insertion of a page/folio with a page index of ULONG_MAX into the page cache via the GC ioctl. filemap_get_folios_tag(), called by nilfs_lookup_dirty_data_buffers(), repeatedly detects a dirty folio with a page index of ULONG_MAX due to index wrap-around, leading to duplicate processing of dirty buffers.  As a preparatory step, the GC ioctl loads the page/folio of the block to be moved during GC and inserts it into the page cache based on information in the nilfs_vdesc structure passed as an argument.  Normally, this does not cause issues because the user-space GC library configures the nilfs_vdesc structure properly.  However, since there is no range check on the parameters determining the page index, a request with artificially crafted parameters -- such as those generated by Syzbot -- can result in a page/folio being inserted with a page index of ULONG_MAX, triggering the above problem.  This resolves the issue by checking the ranges of 'vd_offset' and 'vd_vblocknr' in the nilfs_vdesc structure that determine the page index, thereby preventing the invalid page/folio insertions.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.187-1 | [DEBIAN-CVE-2026-80807](https://patchblox.com/security/data/fix/linux/debian-cve-2026-80807.md) | Sep 5, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.111-1 | [DEBIAN-CVE-2026-80807](https://patchblox.com/security/data/fix/linux/debian-cve-2026-80807.md) | Sep 5, 2026 |
| Linux | linux Debian 14 | 7.1.12-1 | [DEBIAN-CVE-2026-80807](https://patchblox.com/security/data/fix/linux/debian-cve-2026-80807.md) | Sep 5, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.111-1~deb12u1 | [DEBIAN-CVE-2026-80807](https://patchblox.com/security/data/fix/linux/debian-cve-2026-80807.md) | Sep 5, 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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