{"id":"CVE-2026-55517","sourceIdentifier":"security-advisories@github.com","published":"2026-06-23T18:18:09.787","lastModified":"2026-06-29T13:27:11.020","vulnStatus":"Analyzed","cveTags":[],"descriptions":[{"lang":"en","value":"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":[{"source":"security-advisories@github.com","affectedData":[{"vendor":"denoland","product":"deno","versions":[{"version":"< 2.7.5","status":"affected"}]}]}],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","baseScore":4.3,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"LOW"},"exploitabilityScore":2.8,"impactScore":1.4}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-06-23T17:52:15.311461Z","id":"CVE-2026-55517","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"security-advisories@github.com","type":"Primary","description":[{"lang":"en","value":"CWE-248"}]}],"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:deno:deno:*:*:*:*:*:*:*:*","versionEndExcluding":"2.7.5","matchCriteriaId":"D23838A8-D7D0-462F-8B7D-C33526ABD5FB"}]}]}],"references":[{"url":"https://github.com/denoland/deno/security/advisories/GHSA-x2qc-cmh9-f4hf","source":"security-advisories@github.com","tags":["Mitigation","Vendor Advisory"]}]}