Improper Handling of Syntactically Invalid Structure Affecting msgpack5 package, versions <6.1.0
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-JS-MSGPACK5-20581802
- published8 Oct 2026
- disclosed8 Oct 2026
- creditSWIFI AI
Introduced: 8 Oct 2026
NewCVE-2026-107299 (opens in a new tab)How to fix?
Upgrade msgpack5 to version 6.1.0 or higher.
Overview
msgpack5 is an A msgpack v5 implementation for node.js and the browser, with extension points
Affected versions of this package are vulnerable to Improper Handling of Syntactically Invalid Structure via the tryDecode function in lib/decoder.js, which does not reject the reserved MessagePack byte 0xc1 before attempting to process it. An attacker can send a message containing this reserved byte to trigger an unhandled error that crashes the stream, causing a denial of service.