CVE-2026-55517: medium-severity vulnerability in denoland deno
Deno: Denial of service via non-ASCII bytes in WebSocket response headers
Published
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 4.3epss 0.3%
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:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
Affected products
denoland · denoRelated CVEs — denoland deno
In the same product, most dangerous first.
CVE-2026-27190HIGHDeno has a Command Injection via Incomplete shell metacharacter blocklist in node:child_processEPSS 2.5%CVE-2024-27933HIGHDeno arbitrary file descriptor close via `op_node_ipc_pipe()` leading to permission prompt bypassEPSS 2.3%CVE-2025-61787HIGHDeno is Vulnerable to Command Injection on Windows During Batch File ExecutionEPSS 2.1%CVE-2026-32260HIGHCommand Injection via incomplete shell metacharacter blocklist in node:child_process (bypass of CVE-2026-27190 fix)EPSS 1.6%CVE-2026-103473CRITICALDeno 2.7.0 through 2.9.7 Command Injection via node:child_processEPSS 1.5%CVE-2022-24783CRITICALSandbox bypass leading to arbitrary code execution in DenoEPSS 1.1%