# CVE-2024-50217: btrfs: fix use-after-free of block device file in __btrfs_free_extra_devids()

> A use-after-free in the Linux kernel btrfs filesystem allows local attackers to potentially execute code or escalate privileges via crafted mount sequences.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 9 Nov 2024
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-53057, AZL-53096, BELL-CVE-2024-50217, DEBIAN-CVE-2024-50217, GHSA-5684-4xfg-mxj4, ROOT-OS-DEBIAN-11-CVE-2024-50217, ROOT-OS-DEBIAN-12-CVE-2024-50217, ROOT-OS-UBUNTU-2204-CVE-2024-50217, ROOT-OS-UBUNTU-2404-CVE-2024-50217, UBUNTU-CVE-2024-50217

## What is CVE-2024-50217?

CVE-2024-50217 is a high-severity use after free vulnerability in Linux kernel, published on 9 Nov 2024. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

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

btrfs: fix use-after-free of block device file in __btrfs_free_extra_devids()

Mounting btrfs from two images (which have the same one fsid and two
different dev_uuids) in certain executing order may trigger an UAF for
variable 'device->bdev_file' in __btrfs_free_extra_devids(). And
following are the details:

1. Attach image_1 to loop0, attach image_2 to loop1, and scan btrfs
   devices by ioctl(BTRFS_IOC_SCAN_DEV):

             /  btrfs_device_1 → loop0
   fs_device
             \  btrfs_device_2 → loop1
2. mount /dev/loop0 /mnt
   btrfs_open_devices
    btrfs_device_1->bdev_file = btrfs_get_bdev_and_sb(loop0)
    btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1)
   btrfs_fill_super
    open_ctree
     fail: btrfs_close_devices // -ENOMEM
	    btrfs_close_bdev(btrfs_device_1)
             fput(btrfs_device_1->bdev_file)
	      // btrfs_device_1->bdev_file is freed
	    btrfs_close_bdev(btrfs_device_2)
             fput(btrfs_device_2->bdev_file)

3. mount /dev/loop1 /mnt
   btrfs_open_devices
    btrfs_get_bdev_and_sb(&bdev_file)
     // EIO, btrfs_device_1->bdev_file is not assigned,
     // which points to a freed memory area
    btrfs_device_2->bdev_file = btrfs_get_bdev_and_sb(loop1)
   btrfs_fill_super
    open_ctree
     btrfs_free_extra_devids
      if (btrfs_device_1->bdev_file)
       fput(btrfs_device_1->bdev_file) // UAF !

Fix it by setting 'device->bdev_file' as 'NULL' after closing the
btrfs_device in btrfs_close_one_device().

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2024-50217?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-50217?

Apply the vendor's patch.

## Is CVE-2024-50217 being exploited?

There is no known exploitation of CVE-2024-50217 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-2024-50217 and fix it if it is affected.

What it is: CVE-2024-50217 is a high-severity use after free vulnerability in Linux kernel, published on 9 Nov 2024. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2024-50217 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-2024-50217/ (Markdown: https://insights.sbomify.com/CVE-2024-50217/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-50217
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-50217
- OSV: https://osv.dev/vulnerability/CVE-2024-50217

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-50217/
Summaries are generated and may contain mistakes; the official description above is the record.