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Medium severity4.3NVD Advisory· Published Jun 23, 2026· Updated Jun 29, 2026

CVE-2026-55517

CVE-2026-55517

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.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
denocrates.io
< 2.7.52.7.5

Affected products

3
  • Denoland/Denollm-create2 versions
    <2.7.5+ 1 more
    • (no CPE)range: <2.7.5
    • cpe:2.3:a:deno:deno:*:*:*:*:*:*:*:*range: <2.7.5
  • ghsa-coords
    pkg:cargo/deno
    Range: < 2.7.5

Patches

Vulnerability mechanics

References

2

News mentions

1