# CVE-2023-35838: Misconfiguration in n/a

> An attacker can trick WireGuard users into blocking traffic to specific non-RFC1918 IP addresses, causing a denial of service for those services.

- **Severity:** Medium 5.7 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 9 Aug 2023
- **Updated:** 18 Oct 2024
- **Also known as:** GHSA-q424-r5hc-33qq, PYSEC-2023-321, UBUNTU-CVE-2023-35838

## What is CVE-2023-35838?

CVE-2023-35838 is a medium-severity vulnerability in n/a, published on 9 Aug 2023. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

The WireGuard client 0.5.3 on Windows insecurely configures the operating system and firewall such that traffic to a local network that uses non-RFC1918 IP addresses is blocked. This allows an adversary to trick the victim into blocking IP traffic to selected IP addresses and services even while the VPN is enabled. NOTE: the tunnelcrack.mathyvanhoef.com website uses this CVE ID to refer more generally to "LocalNet attack resulting in the blocking of traffic" rather than to only WireGuard.

Weakness: CWE-610 (Externally Controlled Reference to a Resource in Another Sphere)

## Which versions are affected by CVE-2023-35838?

1 open source package ship an affected version, including wireguard. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `wireguard` | PyPI | All versions to 0.5.3 | None |

Products: Wireguard Wireguard.

## How do I fix CVE-2023-35838?

No fix has been published for CVE-2023-35838 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-35838 being exploited?

There is no known exploitation of CVE-2023-35838 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-46873](https://insights.sbomify.com/CVE-2021-46873/): Race condition in n/a (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-35838 and fix it if it is affected.

What it is: CVE-2023-35838 is a medium-severity vulnerability in n/a, published on 9 Aug 2023. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2023-35838 in the wild and no public exploit code.

Affected packages and fixed versions:
- wireguard (PyPI): affected all versions up to 0.5.3; no fix listed

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-2023-35838/ (Markdown: https://insights.sbomify.com/CVE-2023-35838/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-35838
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-35838
- OSV: https://osv.dev/vulnerability/CVE-2023-35838

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-35838/
Summaries are generated and may contain mistakes; the official description above is the record.