Modification of Assumed-Immutable Data (MAID) 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-MSGPACK5-20581674
- published8 Oct 2026
- disclosed8 Oct 2026
- creditSWIFI AI
Introduced: 8 Oct 2026
NewCVE-2026-107296 (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 Modification of Assumed-Immutable Data (MAID) via the readInt64BE function in lib/decoder.js, which mutates the input buffer in-place when decoding a negative 64-bit signed integer. An attacker who can supply a msgpack payload containing a negative int64 value can cause the underlying buffer to be modified during decoding, allowing unintended alteration of shared buffer data and producing an incorrect decoded result.