CVE-2026-55517
Deno: Denial of service via non-ASCII bytes in WebSocket response headers
- State
- Published
- Severity
- 4.3 Medium
- Published
- Jun 23, 2026
- Updated
- Jun 23, 2026
- Reserved
- Jun 16, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 4.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L | GitHub_M |
Weaknesses
- CWE-248 Uncaught Exception
Affected Products
| Product | Versions |
|---|---|
denodenoland |
|
References
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