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

Not scored Published 4 Sep 2026 Updated 19 Oct 2026

A local attacker can trigger a denial of service in the Linux kernel nilfs2 filesystem by exploiting an integer overflow in the GC ioctl.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-80807?

CVE-2026-80807 is a vulnerability in Linux, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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.

Which versions are affected by CVE-2026-80807?

How do I fix CVE-2026-80807?

Apply the vendor's patch.

Is CVE-2026-80807 being exploited?

There is no known exploitation of CVE-2026-80807 in the wild and no public exploit code.

Sources

Also known as AZL-99510, BELL-CVE-2026-80807, DEBIAN-CVE-2026-80807, GHSA-h6ww-mgj9-p3pf, UBUNTU-CVE-2026-80807.