# CVE-2026-98240: net: ip_tunnel: initialize `options_len` before referencing options

> A local attacker can trigger a kernel panic via specific IP tunnel configuration commands, causing a denial of service.

- **Severity:** Not scored
- **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:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98240, DEBIAN-CVE-2026-98240, GHSA-2fq7-gw6w-f3qv, UBUNTU-CVE-2026-98240

## What is CVE-2026-98240?

CVE-2026-98240 is a memory corruption vulnerability in Linux, published on 6 Oct 2026. 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:

net: ip_tunnel: initialize `options_len` before referencing options

The following command triggers a kernel panic:

  ip link add d0 type dummy; ip link set d0 up
  ip route add 10.30.0.0/16 \
    encap ip id 300 geneve_opts 4660:66:11223344 dev d0

  memcpy: detected buffer overflow: 4 byte write of buffer size 0
  kernel BUG at lib/string_helpers.c:1044!
  ...
  ip_tun_parse_opts.part.0.cold+0x10/0x10
  ip_tun_build_state+0x116/0x2a0

On kernels built with GCC 15+ and `CONFIG_FORTIFY_SOURCE`, the fortified
`memcpy()` got 0 sized destination with request of 4 bytes length:

  static int ip_tun_parse_opts_geneve(...)
  {
      ...
      attr = tb[LWTUNNEL_IP_OPT_GENEVE_DATA];
      data_len = nla_len(attr); /* == 4 */

      struct geneve_opt *opt = ip_tunnel_info_opts(info) + opts_len;
      memcpy(opt->opt_data, nla_data(attr), data_len);
      /*     ^^^^^^^^^^^^^ 0 since options_len is assigned afterwards */

Fixed by initializing the counter before the options are referenced.
Matching what `tunnel_key_opts_set()` already does.

## Which versions are affected by CVE-2026-98240?


## How do I fix CVE-2026-98240?

Apply the vendor's patch.

## Is CVE-2026-98240 being exploited?

There is no known exploitation of CVE-2026-98240 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98240 and fix it if it is affected.

What it is: CVE-2026-98240 is a memory corruption vulnerability in Linux, published on 6 Oct 2026. 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-2026-98240 in the wild and no public exploit code.

Affected product: 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-2026-98240/ (Markdown: https://insights.sbomify.com/CVE-2026-98240/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98240
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98240
- OSV: https://osv.dev/vulnerability/CVE-2026-98240

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98240/
Summaries are generated and may contain mistakes; the official description above is the record.