{"id":"CVE-2026-55517","title":"Deno is a JavaScript, TypeScript, and WebAssembly runtime","summary":"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 Se…","severity":"medium","cvss":4.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","cwe":["CWE-248"],"published":"2026-06-23","updated":"2026-06-29","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-55517","references":[{"url":"https://github.com/denoland/deno/security/advisories/GHSA-x2qc-cmh9-f4hf","label":"security-advisories@github.com"}],"tags":["nvd"],"epss":0.00315,"epssPercentile":0.21726,"ingestedAt":"2026-06-29T13:42:11.982Z","slug":"CVE-2026-55517","body":"## Overview\n\nDeno 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":24,"depthScoreParts":{"impact":23.7,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}