# CVE-2026-43158: xfs: fix freemap adjustments when adding xattrs to leaf blocks

> A flaw in the Linux kernel XFS filesystem allows local attackers to trigger a filesystem shutdown via memory corruption during extended attribute operations.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-43158, DEBIAN-CVE-2026-43158, GHSA-j4pf-wvpf-rv38, ROOT-OS-DEBIAN-11-CVE-2026-43158, ROOT-OS-UBUNTU-2204-CVE-2026-43158, ROOT-OS-UBUNTU-2404-CVE-2026-43158, UBUNTU-CVE-2026-43158

## What is CVE-2026-43158?

CVE-2026-43158 is a high-severity memory corruption vulnerability in Linux kernel, published on 6 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

xfs: fix freemap adjustments when adding xattrs to leaf blocks

xfs/592 and xfs/794 both trip this assertion in the leaf block freemap
adjustment code after ~20 minutes of running on my test VMs:

 ASSERT(ichdr->firstused >= ichdr->count * sizeof(xfs_attr_leaf_entry_t)
					+ xfs_attr3_leaf_hdr_size(leaf));

Upon enabling quite a lot more debugging code, I narrowed this down to
fsstress trying to set a local extended attribute with namelen=3 and
valuelen=71.  This results in an entry size of 80 bytes.

At the start of xfs_attr3_leaf_add_work, the freemap looks like this:

i 0 base 448 size 0 rhs 448 count 46
i 1 base 388 size 132 rhs 448 count 46
i 2 base 2120 size 4 rhs 448 count 46
firstused = 520

where "rhs" is the first byte past the end of the leaf entry array.
This is inconsistent -- the entries array ends at byte 448, but
freemap[1] says there's free space starting at byte 388!

By the end of the function, the freemap is in worse shape:

i 0 base 456 size 0 rhs 456 count 47
i 1 base 388 size 52 rhs 456 count 47
i 2 base 2120 size 4 rhs 456 count 47
firstused = 440

Important note: 388 is not aligned with the entries array element size
of 8 bytes.

Based on the incorrect freemap, the name area starts at byte 440, which
is below the end of the entries array!  That's why the assertion
triggers and the filesystem shuts down.

How did we end up here?  First, recall from the previous patch that the
freemap array in an xattr leaf block is not intended to be a
comprehensive map of all free space in the leaf block.  In other words,
it's perfectly legal to have a leaf block with:

 * 376 bytes in use by the entries array
 * freemap[0] has [base = 376, size = 8]
 * freemap[1] has [base = 388, size = 1500]
 * the space between 376 and 388 is free, but the freemap stopped
   tracking that some time ago

If we add one xattr, the entries array grows to 384 bytes, and
freemap[0] becomes [base = 384, size = 0].  So far, so good.  But if we
add a second xattr, the entries array grows to 392 bytes, and freemap[0]
gets pushed up to [base = 392, size = 0].  This is bad, because
freemap[1] hasn't been updated, and now the entries array and the free
space claim the same space.

The fix here is to adjust all freemap entries so that none of them
collide with the entries array.  Note that this fix relies on commit
2a2b5932db6758 ("xfs: fix attr leaf header freemap.size underflow") and
the previous patch that resets zero length freemap entries to have
base = 0.

Weakness: CWE-787 (Out-of-bounds Write), CWE-664 (Improper Control of a Resource Through its Lifetime)

## Which versions are affected by CVE-2026-43158?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43158?

Apply the vendor's patch.

## Is CVE-2026-43158 being exploited?

There is no known exploitation of CVE-2026-43158 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-2026-43158 and fix it if it is affected.

What it is: CVE-2026-43158 is a high-severity memory corruption vulnerability in Linux kernel, published on 6 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-43158 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-2026-43158/ (Markdown: https://insights.sbomify.com/CVE-2026-43158/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43158
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43158
- OSV: https://osv.dev/vulnerability/CVE-2026-43158

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43158/
Summaries are generated and may contain mistakes; the official description above is the record.