# CVE-2024-44963: btrfs: do not BUG_ON() when freeing tree block after error

> A local attacker can trigger a kernel crash by causing a memory allocation failure during Btrfs tree block freeing, leading to denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 4 Sep 2024
- **Updated:** 11 May 2026
- **Also known as:** AZL-49924, AZL-49953, BELL-CVE-2024-44963, DEBIAN-CVE-2024-44963, GHSA-9388-m6c7-2394, ROOT-OS-DEBIAN-11-CVE-2024-44963, ROOT-OS-DEBIAN-12-CVE-2024-44963, ROOT-OS-UBUNTU-2204-CVE-2024-44963, UBUNTU-CVE-2024-44963

## What is CVE-2024-44963?

CVE-2024-44963 is a medium-severity denial of service vulnerability in Linux kernel, published on 4 Sep 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:

btrfs: do not BUG_ON() when freeing tree block after error

When freeing a tree block, at btrfs_free_tree_block(), if we fail to
create a delayed reference we don't deal with the error and just do a
BUG_ON(). The error most likely to happen is -ENOMEM, and we have a
comment mentioning that only -ENOMEM can happen, but that is not true,
because in case qgroups are enabled any error returned from
btrfs_qgroup_trace_extent_post() (can be -EUCLEAN or anything returned
from btrfs_search_slot() for example) can be propagated back to
btrfs_free_tree_block().

So stop doing a BUG_ON() and return the error to the callers and make
them abort the transaction to prevent leaking space. Syzbot was
triggering this, likely due to memory allocation failure injection.

## Which versions are affected by CVE-2024-44963?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-44963?

Apply the vendor's patch.

## Is CVE-2024-44963 being exploited?

There is no known exploitation of CVE-2024-44963 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-2024-44963 and fix it if it is affected.

What it is: CVE-2024-44963 is a medium-severity denial of service vulnerability in Linux kernel, published on 4 Sep 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-2024-44963 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-2024-44963/ (Markdown: https://insights.sbomify.com/CVE-2024-44963/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-44963
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-44963
- OSV: https://osv.dev/vulnerability/CVE-2024-44963

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-44963/
Summaries are generated and may contain mistakes; the official description above is the record.