CVE-2023-36673

CVE-2023-36673 is a high-severity vulnerability in Avira Phantom Vpn with a CVSS 3.x base score of 7.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-319.

Key facts

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2023-36673?
CVE-2023-36673 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2023-36673 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-36673?
CVE-2023-36673 affects Avira Phantom Vpn. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2023-36673?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2023-36673 published?
CVE-2023-36673 was published on 2023-08-09 and last updated on 2026-06-17.

References

Affected products (1)

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