# 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.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 May 2026
- **Updated:** 19 Oct 2026
- **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

## 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 (Improper Input Validation)

## Which versions are affected by CVE-2026-43365?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43365?

Apply the vendor's patch.

## 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

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43365 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-43365 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-43365/ (Markdown: https://insights.sbomify.com/CVE-2026-43365/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43365
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43365
- OSV: https://osv.dev/vulnerability/CVE-2026-43365

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43365/
Summaries are generated and may contain mistakes; the official description above is the record.