Impact

The Cloudflare WARP client for Windows assigns loopback IPv4 addresses for the DNS Servers, since WARP acts as local DNS server that performs DNS queries in a secure manner, however, if a user is connected to WARP over an IPv6-capable network, te WARP client did not assign loopback IPv6 addresses but Unique Local Addresses, which under certain conditions could point towards unknown devices in the same local network which enables an Attacker to view DNS queries made by the device.

Requirements

• The victim's device would need to be connected to a rogue Wi-Fi network, that announces support for IPv6, and assigns itself the same IPv6 address that WARP Client sets the IPv6 DNS server as.

Patches

Version 2023.7.160.0 for WARP Client (Windows)

Workarounds

Disabling IPv6 support in local devices

References

WARP Client Releases
WARP Client Documentation
CVE Advisory
HackerOne Report