CVE-2023-36673

Published: 9 August 2023

An issue was discovered in Avira Phantom VPN through 2.23.1 for macOS. The VPN client insecurely configures the operating system such that all IP traffic to the VPN server's IP address is sent in plaintext outside the VPN tunnel, even if this traffic is not generated by the VPN client, while simultaneously using plaintext DNS to look up the VPN server's IP address. This allows an adversary to trick the victim into sending traffic to arbitrary IP addresses in plaintext outside the VPN tunnel. NOTE: the tunnelcrack.mathyvanhoef.com website uses this CVE ID to refer more generally to "ServerIP attack, combined with DNS spoofing, that can leak traffic to an arbitrary IP address" rather than to only Avira Phantom VPN.

Notes

other VPN software may also be affected. See whitepaper for the
complete list.

as of 2024-02-05, there doesn't appear to be an upstream fix
available for network-manager-openvpn, openvpn packages.
as of 2024-02-29, there doesn't appear to be an upstream fix
available for network-manager-pptp, pptp-linux.

as of 2024-04-15, this CVE appears to be specific to the
Avira Phantom VPN, marking all Ubuntu packages as not-affected

Status

Severity score breakdown

References

• https://tunnelcrack.mathyvanhoef.com/details.html
• https://papers.mathyvanhoef.com/usenix2023-tunnelcrack.pdf
• https://openvpn.net/security-advisory/statement-regarding-tunnelcrack-vulnerabilities/
• https://www.softether.org/9-about/News/905-TunnelCrack
• https://www.cve.org/CVERecord?id=CVE-2023-36673
• NVD
• Launchpad
• Debian