CVE-2026-90259 btrfs: qgroup: fix a wrong length calculation in qgroup_free_reserved_data()
A logic error in the Linux kernel's btrfs filesystem causes incorrect length calculations, potentially leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90259?
CVE-2026-90259 is a vulnerability in Linux, published on 17 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:
btrfs: qgroup: fix a wrong length calculation in qgroup_free_reserved_data()
In that function, we round down the start position and round up the ending position.
But during the calculation of @len, we use "round_up(start + len, sectorsize)", which is the rounded up end position, not the rounded up length.
Which results a much larger length, and later we are still using "start + len", which is completely incorrect.
Fix it by declaring a local @aligned_start and @aligned_len and use them instead.
Which versions are affected by CVE-2026-90259?
How do I fix CVE-2026-90259?
Apply the vendor's patch.
Is CVE-2026-90259 being exploited?
There is no known exploitation of CVE-2026-90259 in the wild and no public exploit code.
Sources
Also known as AZL-102108, BELL-CVE-2026-90259, DEBIAN-CVE-2026-90259, GHSA-m2j4-9jh2-f83w, UBUNTU-CVE-2026-90259.