CVE-2026-55517
MEDIUM severity · CVSS 4.3 · CWE-248
4.3CVSS MEDIUM
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 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.
Impact & exploitability
Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionRequired
Confidentiality impactNone
Integrity impactNone
Availability impactLow
Exploit probability (EPSS)0%
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
Affected products we track (1)
Recommendation
Apply the vendor fix in your normal patch cycle. Open any affected product above for its exact safe version.