# CVE-2024-26665: tunnels: fix out of bounds access when building IPv6 PMTU error

> A remote attacker can cause a kernel crash via out-of-bounds read in IPv6 tunnel PMTU error handling.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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:** 2 Apr 2024
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2024-26665, DEBIAN-CVE-2024-26665, GHSA-qg9h-x99x-fcvh, UBUNTU-CVE-2024-26665

## What is CVE-2024-26665?

CVE-2024-26665 is a critical memory corruption vulnerability in Debian Debian Linux, published on 2 Apr 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:

tunnels: fix out of bounds access when building IPv6 PMTU error

If the ICMPv6 error is built from a non-linear skb we get the following
splat,

  BUG: KASAN: slab-out-of-bounds in do_csum+0x220/0x240
  Read of size 4 at addr ffff88811d402c80 by task netperf/820
  CPU: 0 PID: 820 Comm: netperf Not tainted 6.8.0-rc1+ #543
  ...
   kasan_report+0xd8/0x110
   do_csum+0x220/0x240
   csum_partial+0xc/0x20
   skb_tunnel_check_pmtu+0xeb9/0x3280
   vxlan_xmit_one+0x14c2/0x4080
   vxlan_xmit+0xf61/0x5c00
   dev_hard_start_xmit+0xfb/0x510
   __dev_queue_xmit+0x7cd/0x32a0
   br_dev_queue_push_xmit+0x39d/0x6a0

Use skb_checksum instead of csum_partial who cannot deal with non-linear
SKBs.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2024-26665?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2024-26665?

Apply the vendor's patch.

## Is CVE-2024-26665 being exploited?

There is no known exploitation of CVE-2024-26665 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-26665 and fix it if it is affected.

What it is: CVE-2024-26665 is a critical memory corruption vulnerability in Debian Debian Linux, published on 2 Apr 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-2024-26665 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2024-26665/ (Markdown: https://insights.sbomify.com/CVE-2024-26665/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-26665
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-26665
- OSV: https://osv.dev/vulnerability/CVE-2024-26665

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-26665/
Summaries are generated and may contain mistakes; the official description above is the record.