CVE-2020-7663: Canonical Ubuntu Linux

High severity, CVSS 7.5. EPSS: 4.5% chance of exploitation in the next 30 days.

websocket-extensions ruby module prior to 0.1.5 allows Denial of Service (DoS) via Regex Backtracking. The extension parser may take quadratic time when parsing a header containing an unclosed string parameter value whose content is a repeating two-byte sequence of a backslash and some other character. This could be abused by an attacker to conduct Regex Denial Of Service (ReDoS) on a single-threaded server by providing a malicious payload with the Sec-WebSocket-Extensions header.

Affected products

• Canonical Ubuntu Linux: version 16.04 only; version 18.04 only; version 20.04 only
• Debian Debian Linux: version 9.0 only
• Websocket-Extensions Project Websocket-Extensions: before 0.1.5 (fixed in 0.1.5)

Published 2020-06-02. Last modified 2026-06-17.