CVE-2025-10148

curl's WebSocket code did not update the 32-bit mask pattern for each new

outgoing frame as the specification says. Instead it used a fixed mask that

persisted and was used throughout the entire connection.

A predictable mask pattern allows for a malicious server to induce traffic

between the two communicating parties that could be interpreted by an involved

proxy (configured or transparent) as genuine, real, HTTP traffic with content

and thereby poison its cache. That cached poisoned content could then be

served to all users of that proxy.