CVE-2023-36673

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 servers 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 servers 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.

Weakness

The product transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors.

Affected Software

Extended Description

Many communication channels can be “sniffed” (monitored) by adversaries during data transmission. For example, in networking, packets can traverse many intermediary nodes from the source to the destination, whether across the internet, an internal network, the cloud, etc. Some actors might have privileged access to a network interface or any link along the channel, such as a router, but they might not be authorized to collect the underlying data. As a result, network traffic could be sniffed by adversaries, spilling security-critical data. Applicable communication channels are not limited to software products. Applicable channels include hardware-specific technologies such as internal hardware networks and external debug channels, supporting remote JTAG debugging. When mitigations are not applied to combat adversaries within the product’s threat model, this weakness significantly lowers the difficulty of exploitation by such adversaries. When full communications are recorded or logged, such as with a packet dump, an adversary could attempt to obtain the dump long after the transmission has occurred and try to “sniff” the cleartext from the recorded communications in the dump itself.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/102.html
• https://cwe.mitre.org/data/definitions/117.html
• https://cwe.mitre.org/data/definitions/383.html
• https://cwe.mitre.org/data/definitions/477.html
• https://cwe.mitre.org/data/definitions/65.html

References

• https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2023-0015
• https://tunnelcrack.mathyvanhoef.com/details.html
• https://www.avira.com/en/free-vpn
• https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2023-0015
• https://tunnelcrack.mathyvanhoef.com/details.html
• https://www.avira.com/en/free-vpn