CVE-2026-107300: msgpack5: Many buffered values can exhaust the streaming decoder stack

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-08 · updated 2026-10-08
Weakness: CWE-674

Description

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder recursively invokes itself for each complete MessagePack value remaining in a chunk. A remote peer can send one chunk containing many small valid values, causing recursion proportional to the value count, exhausting the JavaScript call stack, and interrupting the process or stream. This issue is fixed in version 6.1.0.

Affected products

mcollina msgpack5: before 6.1.0

References

https://github.com/mcollina/msgpack5/commit/77fbef144d05def5d16fc22c37caa64c0a7efeba
https://github.com/mcollina/msgpack5/releases/tag/v6.1.0
https://github.com/mcollina/msgpack5/security/advisories/GHSA-5x5g-h9x8-2fh9

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