# CVE-2024-49855: nbd: fix race between timeout and normal completion

> A race condition in the Linux kernel NBD driver can lead to a use-after-free, potentially allowing local attackers to execute code or escalate privileges.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Oct 2024
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-50640, BELL-CVE-2024-49855, DEBIAN-CVE-2024-49855, GHSA-x6h6-973g-q656, ROOT-OS-UBUNTU-2204-CVE-2024-49855, UBUNTU-CVE-2024-49855

## What is CVE-2024-49855?

CVE-2024-49855 is a critical use after free vulnerability in Linux kernel, published on 21 Oct 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

nbd: fix race between timeout and normal completion

If request timetout is handled by nbd_requeue_cmd(), normal completion
has to be stopped for avoiding to complete this requeued request, other
use-after-free can be triggered.

Fix the race by clearing NBD_CMD_INFLIGHT in nbd_requeue_cmd(), meantime
make sure that cmd->lock is grabbed for clearing the flag and the
requeue.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2024-49855?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-49855?

Apply the vendor's patch.

## Is CVE-2024-49855 being exploited?

There is no known exploitation of CVE-2024-49855 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-2024-49855 and fix it if it is affected.

What it is: CVE-2024-49855 is a critical use after free vulnerability in Linux kernel, published on 21 Oct 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-49855 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-2024-49855/ (Markdown: https://insights.sbomify.com/CVE-2024-49855/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-49855
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-49855
- OSV: https://osv.dev/vulnerability/CVE-2024-49855

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-49855/
Summaries are generated and may contain mistakes; the official description above is the record.