CVE-2026-107297: msgpack5: Quadratic parsing in the streaming decoder

October 8, 2026

The streaming decoder reparses an incomplete container from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack value across many small chunks, causing quadratic CPU usage and blocking the event loop.

References

github.com/advisories/GHSA-gcx5-hxj7-gpqq
github.com/mcollina/msgpack5/commit/e4827641d3105e295cbbd56e9c5389978547eab4
github.com/mcollina/msgpack5/releases/tag/v6.1.0
github.com/mcollina/msgpack5/security/advisories/GHSA-gcx5-hxj7-gpqq
nvd.nist.gov/vuln/detail/CVE-2026-107297

Code Behaviors & Features

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