medium4.3
CVE-2026-55517
Deno: Denial of service via non-ASCII bytes in WebSocket response headers
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| rust | deno | <= 2.7.4 | 2.7.5 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Deno | Deno | before 2.7.5 |