{"cve":"CVE-2026-55517","nvd":{"published":"2026-06-23T18:18:09.787","modified":"2026-10-25T23:10:00.167","status":"Analyzed","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","score":4.3},"cwes":["CWE-248"],"references":["https://github.com/denoland/deno/security/advisories/GHSA-x2qc-cmh9-f4hf"],"products":["deno:deno"],"source":"nvd","synced_at":"2026-10-25T23:44:33.281319194+00:00"},"epss":{"cve":"CVE-2026-55517","score":0.00315,"percentile":0.24193,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-x2qc-cmh9-f4hf","url":"https://osv.dev/vulnerability/GHSA-x2qc-cmh9-f4hf","summary":"Deno: Denial of service via non-ASCII bytes in WebSocket response headers","modified":"2026-06-17T19:11:27.308501Z","packages":[{"ecosystem":"crates.io","name":"deno","purl":"pkg:cargo/deno","ranges":["<2.7.5"],"fixed":["2.7.5"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}