# CVE-2026-74728: xfs: handle NULL b_addr in xfs_buf_free

> A null pointer dereference in the Linux kernel XFS filesystem can cause a system crash when buffer allocation fails, leading to denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Aug 2026
- **Updated:** 21 Oct 2026
- **Also known as:** BELL-CVE-2026-74728, DEBIAN-CVE-2026-74728, GHSA-rrpq-4xmf-c84j, UBUNTU-CVE-2026-74728

## What is CVE-2026-74728?

CVE-2026-74728 is a vulnerability in Linux, published on 22 Aug 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:

xfs: handle NULL b_addr in xfs_buf_free

When xfs_buf_alloc_backing_mem() fails, xfs_buf_free() is called with
bp->b_addr still NULL.  The code falls through to the folio_put path
which calls virt_to_folio(NULL), dereferencing an invalid address and
causing a kernel crash.

 Call Trace:
  xfs_buf_free+0x25f/0x510
  xfs_buf_alloc+0xc98/0x19b0
  xfs_buf_find_insert+0x55/0x14d0
  xfs_buf_get_map+0x122b/0x17c0
  xfbtree_init_leaf_block+0x11c/0x4a0
  xfbtree_init+0x1bb/0x460
  xrep_rmap_setup_scan+0x100/0x1f0
  xrep_rmapbt+0x41/0xc0

Fix this by skipping folio_put() when bp->b_addr is NULL.

## Which versions are affected by CVE-2026-74728?


## How do I fix CVE-2026-74728?

Apply the vendor's patch.

## Is CVE-2026-74728 being exploited?

There is no known exploitation of CVE-2026-74728 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74728 and fix it if it is affected.

What it is: CVE-2026-74728 is a vulnerability in Linux, published on 22 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74728 in the wild and no public exploit code.

Affected product: Linux. 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-2026-74728/ (Markdown: https://insights.sbomify.com/CVE-2026-74728/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74728
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74728
- OSV: https://osv.dev/vulnerability/CVE-2026-74728

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74728/
Summaries are generated and may contain mistakes; the official description above is the record.