# CVE-2024-49987: bpftool: Fix undefined behavior in qsort(NULL, 0, ...)

> A null pointer dereference in bpftool when displaying empty netfilter entries can cause a crash, requiring a kernel patch.

- **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:** 21 Oct 2024
- **Updated:** 11 May 2026
- **Also known as:** AZL-51768, BELL-CVE-2024-49987, DEBIAN-CVE-2024-49987, GHSA-qf5q-fm5c-hc2p, ROOT-OS-DEBIAN-12-CVE-2024-49987, ROOT-OS-UBUNTU-2204-CVE-2024-49987, SUSE-SU-2024:4157-1, UBUNTU-CVE-2024-49987

## What is CVE-2024-49987?

CVE-2024-49987 is a medium-severity vulnerability in Linux kernel, published on 21 Oct 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:

bpftool: Fix undefined behavior in qsort(NULL, 0, ...)

When netfilter has no entry to display, qsort is called with
qsort(NULL, 0, ...). This results in undefined behavior, as UBSan
reports:

net.c:827:2: runtime error: null pointer passed as argument 1, which is declared to never be null

Although the C standard does not explicitly state whether calling qsort
with a NULL pointer when the size is 0 constitutes undefined behavior,
Section 7.1.4 of the C standard (Use of library functions) mentions:

"Each of the following statements applies unless explicitly stated
otherwise in the detailed descriptions that follow: If an argument to a
function has an invalid value (such as a value outside the domain of
the function, or a pointer outside the address space of the program, or
a null pointer, or a pointer to non-modifiable storage when the
corresponding parameter is not const-qualified) or a type (after
promotion) not expected by a function with variable number of
arguments, the behavior is undefined."

To avoid this, add an early return when nf_link_info is NULL to prevent
calling qsort with a NULL pointer.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2024-49987?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `bpftool` | SUSE:Linux Enterprise Module for Basesystem 15 SP6 | All versions | 6.4.0-150600.19.6.1 |
| `bpftool` | openSUSE:Leap 15.6 | All versions | 6.4.0-150600.19.6.1 |

Products: Linux kernel.

## How do I fix CVE-2024-49987?

Apply the vendor's patch.

## Is CVE-2024-49987 being exploited?

There is no known exploitation of CVE-2024-49987 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-2024-49987 and fix it if it is affected.

What it is: CVE-2024-49987 is a medium-severity vulnerability in Linux kernel, published on 21 Oct 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-2024-49987 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-2024-49987/ (Markdown: https://insights.sbomify.com/CVE-2024-49987/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-49987
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-49987
- OSV: https://osv.dev/vulnerability/CVE-2024-49987

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-49987/
Summaries are generated and may contain mistakes; the official description above is the record.