# CVE-2024-36937: xdp: use flags field to disambiguate broadcast redirect

> A race condition in Linux kernel XDP broadcast redirects can cause a NULL pointer dereference and system crash.

- **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:** 30 May 2024
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2024-36937, DEBIAN-CVE-2024-36937, UBUNTU-CVE-2024-36937

## What is CVE-2024-36937?

CVE-2024-36937 is a medium-severity vulnerability in Linux kernel, published on 30 May 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:

xdp: use flags field to disambiguate broadcast redirect

When redirecting a packet using XDP, the bpf_redirect_map() helper will set
up the redirect destination information in struct bpf_redirect_info (using
the __bpf_xdp_redirect_map() helper function), and the xdp_do_redirect()
function will read this information after the XDP program returns and pass
the frame on to the right redirect destination.

When using the BPF_F_BROADCAST flag to do multicast redirect to a whole
map, __bpf_xdp_redirect_map() sets the 'map' pointer in struct
bpf_redirect_info to point to the destination map to be broadcast. And
xdp_do_redirect() reacts to the value of this map pointer to decide whether
it's dealing with a broadcast or a single-value redirect. However, if the
destination map is being destroyed before xdp_do_redirect() is called, the
map pointer will be cleared out (by bpf_clear_redirect_map()) without
waiting for any XDP programs to stop running. This causes xdp_do_redirect()
to think that the redirect was to a single target, but the target pointer
is also NULL (since broadcast redirects don't have a single target), so
this causes a crash when a NULL pointer is passed to dev_map_enqueue().

To fix this, change xdp_do_redirect() to react directly to the presence of
the BPF_F_BROADCAST flag in the 'flags' value in struct bpf_redirect_info
to disambiguate between a single-target and a broadcast redirect. And only
read the 'map' pointer if the broadcast flag is set, aborting if that has
been cleared out in the meantime. This prevents the crash, while keeping
the atomic (cmpxchg-based) clearing of the map pointer itself, and without
adding any more checks in the non-broadcast fast path.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2024-36937?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-36937?

Apply the vendor's patch.

## Is CVE-2024-36937 being exploited?

There is no known exploitation of CVE-2024-36937 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-2024-36937 and fix it if it is affected.

What it is: CVE-2024-36937 is a medium-severity vulnerability in Linux kernel, published on 30 May 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-2024-36937 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-2024-36937/ (Markdown: https://insights.sbomify.com/CVE-2024-36937/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-36937
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-36937
- OSV: https://osv.dev/vulnerability/CVE-2024-36937

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-36937/
Summaries are generated and may contain mistakes; the official description above is the record.