CVE-2026-55517 – Deno: Denial of service via non-ASCII bytes in WebSocket response headers

CVE ID :CVE-2026-55517

Published : June 23, 2026, 5:24 p.m. | 19 minutes ago

Description :Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.7.5, a Deno program that opens a client WebSocket connection could be crashed by the remote server. While handling the WebSocket handshake response, Deno parsed the Sec-WebSocket-Protocol and Sec-WebSocket-Extensions response headers in a way that assumed their bytes were always printable ASCII. A response header containing non-visible-ASCII bytes (0x80-0xFF) caused a panic that aborted the entire Deno process. This vulnerability is fixed in 2.7.5.

Severity: 0.0 | NA

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