# CVE-2026-86297: D-Link DIR-605 L2TP Control Message tunnel.c tunnel_set_params off-by-one

> Remote attackers can exploit an off-by-one error in the L2TP parser to potentially execute code or cause denial of service on D-Link DIR-605 routers.

- **Severity:** Critical 9.2 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Sep 2026
- **Updated:** 9 Sep 2026
- **Also known as:** GHSA-fwmj-7xm4-cg9r

## What is CVE-2026-86297?

CVE-2026-86297 is a critical vulnerability in D-Link DIR-605, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was identified in D-Link DIR-605 B1v202WWB03. This issue affects the function tunnel_set_params of the file progs.gpl/pppd.alpha/l2tp/tunnel.c of the component L2TP Control Message Parser. Such manipulation of the argument peer_hostname  leads to off-by-one. The attack may be performed from remote. Attacks of this nature are highly complex. The exploitability is assessed as difficult. The exploit is publicly available and might be used.

Weakness: CWE-193 (Off-by-one Error), CWE-189

## Which versions are affected by CVE-2026-86297?


## How do I fix CVE-2026-86297?

No fix has been published for CVE-2026-86297 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-86297 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-86297 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-86297 and fix it if it is affected.

What it is: CVE-2026-86297 is a critical vulnerability in D-Link DIR-605, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-86297 exists.

Affected product: D-Link DIR-605. 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-2026-86297/ (Markdown: https://insights.sbomify.com/CVE-2026-86297/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-86297
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-86297
- OSV: https://osv.dev/vulnerability/CVE-2026-86297

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-86297/
Summaries are generated and may contain mistakes; the official description above is the record.