CVE-2026-107302: Mcollina MSGPACK5

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the decoder reads the four-byte length of a map32 value before validating that the complete five-byte header is available. A truncated map32 header therefore causes a checked out-of-bounds buffer read and throws RangeError instead of IncompleteBufferError, which can unexpectedly terminate a request, stream, or worker in applications that wait for additional bytes after IncompleteBufferError. There is no adjacent-memory disclosure because the buffer implementation checks bounds. This issue is fixed in version 6.1.0.

Affected products

• Mcollina MSGPACK5: before 6.1.0 (fixed in 6.1.0)

Published 2026-10-08. Last modified 2026-10-08.