CVE-2026-43365 xfs: fix undersized l_iclog_roundoff values
A flaw in the Linux kernel XFS filesystem causes log corruption and mount failures on disks with 4k sectors, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43365?
CVE-2026-43365 is a high-severity denial of service vulnerability in Linux kernel, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
xfs: fix undersized l_iclog_roundoff values
If the superblock doesn't list a log stripe unit, we set the incore log roundoff value to 512. This leads to corrupt logs and unmountable filesystems in generic/617 on a disk with 4k physical sectors...
XFS (sda1): Mounting V5 Filesystem ff3121ca-26e6-4b77-b742-aaff9a449e1c XFS (sda1): Torn write (CRC failure) detected at log block 0x318e. Truncating head block from 0x3197. XFS (sda1): failed to locate log tail XFS (sda1): log mount/recovery failed: error -74 XFS (sda1): log mount failed XFS (sda1): Mounting V5 Filesystem ff3121ca-26e6-4b77-b742-aaff9a449e1c XFS (sda1): Ending clean mount
...on the current xfsprogs for-next which has a broken mkfs. xfs_info shows this...
meta-data=/dev/sda1 isize=512 agcount=4, agsize=644992 blks = sectsz=4096 attr=2, projid32bit=1 = crc=1 finobt=1, sparse=1, rmapbt=1 = reflink=1 bigtime=1 inobtcount=1 nrext64=1 = exchange=1 metadir=1 data = bsize=4096 blocks=2579968, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0, ftype=1, parent=1 log =internal log bsize=4096 blocks=16384, version=2 = sectsz=4096 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 = rgcount=0 rgsize=268435456 extents = zoned=0 start=0 reserved=0
...observe that the log section has sectsz=4096 sunit=0, which means that the roundoff factor is 512, not 4096 as you'd expect. We should fix mkfs not to generate broken filesystems, but anyone can fuzz the ondisk superblock so we should be more cautious. I think the inadequate logic predates commit a6a65fef5ef8d0, but that's clearly going to require a different backport.
Weakness: CWE-20
Which versions are affected by CVE-2026-43365?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43365?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-43365 being exploited?
There is no known exploitation of CVE-2026-43365 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43365, DEBIAN-CVE-2026-43365, GHSA-gf37-6wm7-r3cm, ROOT-OS-UBUNTU-2204-CVE-2026-43365, ROOT-OS-UBUNTU-2404-CVE-2026-43365, UBUNTU-CVE-2026-43365.