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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.
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. This vulnerability involves weaknesses in
This medium-severity vulnerability could be exploited under certain conditions to compromise security controls or access sensitive information. Should be addressed in a timely manner.
Probability of exploitation in the next 30 days · more likely than 41.3% of all CVEs.
Isolate affected systems from untrusted networks until patching is complete
Implement enhanced monitoring for exploitation attempts and unusual behavior