# CVE-2024-56549: cachefiles: Fix NULL pointer dereference in object->file

> A race condition in the Linux kernel's cachefiles module causes a NULL pointer dereference, leading to a denial of service.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Dec 2024
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-55195, BELL-CVE-2024-56549, DEBIAN-CVE-2024-56549, GHSA-hm4v-3pg5-6f5c, UBUNTU-CVE-2024-56549

## What is CVE-2024-56549?

CVE-2024-56549 is a high-severity vulnerability in Linux kernel, published on 27 Dec 2024. 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:

cachefiles: Fix NULL pointer dereference in object->file

At present, the object->file has the NULL pointer dereference problem in
ondemand-mode. The root cause is that the allocated fd and object->file
lifetime are inconsistent, and the user-space invocation to anon_fd uses
object->file. Following is the process that triggers the issue:

	  [write fd]				[umount]
cachefiles_ondemand_fd_write_iter
				       fscache_cookie_state_machine
					 cachefiles_withdraw_cookie
  if (!file) return -ENOBUFS
					   cachefiles_clean_up_object
					     cachefiles_unmark_inode_in_use
					     fput(object->file)
					     object->file = NULL
  // file NULL pointer dereference!
  __cachefiles_write(..., file, ...)

Fix this issue by add an additional reference count to the object->file
before write/llseek, and decrement after it finished.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2024-56549?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-56549?

Apply the vendor's patch.

## Is CVE-2024-56549 being exploited?

There is no known exploitation of CVE-2024-56549 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-2024-56549 and fix it if it is affected.

What it is: CVE-2024-56549 is a high-severity vulnerability in Linux kernel, published on 27 Dec 2024. 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-2024-56549 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-2024-56549/ (Markdown: https://insights.sbomify.com/CVE-2024-56549/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-56549
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-56549
- OSV: https://osv.dev/vulnerability/CVE-2024-56549

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-56549/
Summaries are generated and may contain mistakes; the official description above is the record.