Uncaught Exception Affecting deno package, versions <2.7.5
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-RUST-DENO-17660663
- published27 Jun 2026
- disclosed17 Jun 2026
- creditUnknown
Introduced: 17 Jun 2026
NewCVE-2026-55517 (opens in a new tab)How to fix?
Upgrade deno to version 2.7.5 or higher.
Overview
deno is an a simple, modern and secure runtime for JavaScript and TypeScript that uses V8 and is built in Rust.
Affected versions of this package are vulnerable to Uncaught Exception via the WebSocket handshake response headers Sec-WebSocket-Protocol and Sec-WebSocket-Extensions. An attacker can cause the process to terminate unexpectedly by sending non-ASCII bytes in these headers during the handshake response. This is only exploitable if the application initiates a WebSocket connection to an untrusted or compromised endpoint, or if a man-in-the-middle attacker can inject malicious header bytes into a plaintext ws:// connection.
Workaround
This vulnerability can be mitigated by only connecting to trusted WebSocket endpoints and preferring wss:// (TLS) over ws://.