CVE-2023-36673
An issue was discovered in Avira Phantom VPN through 2.23.1 for macOS. The VPN client insecurely...
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.
Attack profile
How easy it is to exploit
- Attack vector
- Adjacent network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
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.
- Record
CVE-2023-36673- CVSS 3.1
- 7.3 High
CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-319
- Updated
- 2026-11-02
CVE List No score
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.
- Record
CVE-2023-36673- Updated
- 2026-11-02
EUVDEUVD-2023-40616 No score
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.
- Record
EUVD-2023-40616- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-r43q-w67j-2696
An issue was discovered in Avira Phantom VPN through 2.23.1 for macOS. The VPN client insecurely...
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.
- Record
GHSA-r43q-w67j-2696- CVSS 3.1
- 7.3 High
CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-319
- Updated
- 2026-11-02
OSVUBUNTU-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 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.
- Record
UBUNTU-CVE-2023-36673- CVSS 3.1
- 7.3 High
CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| affected | ||
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2023-36673 is a high vulnerability (CVSS 7.3) in Avira Phantom Vpn, published August 9, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.53%, the 45th percentile. No source names a fixed version.