CVE-2026-107297: Mcollina MSGPACK5

Medium severity, CVSS 5.9. 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 streaming decoder reparses an incomplete array or map from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack container across many small chunks, causing completed elements to be decoded repeatedly, producing quadratic CPU use and blocking the event loop. 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.