Disclosure summary
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder treats the reserved MessagePack byte 0xc1 as incomplete input instead of invalid input. When 0xc1 begins a stream, subsequent data remains buffered while the decoder waits for bytes that cannot make the value valid, allowing a remote peer to exhaust memory. This issue is fixed in version 6.1.0.
Source-reported weakness categories
CWE-228
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
NIST National Vulnerability Database · NVD-CVE-2026-107299
Open original source · Updated Oct 09, 2026
Only CPE matches marked vulnerable=true are indexed. AND/OR platform conditions must be checked in the original NVD record.
GitHub Reviewed Security Advisories · GHSA-26wq-p25c-j6fv
Open original source · Updated Oct 08, 2026
msgpack5: Reserved byte can cause unbounded stream buffering
Source severity: MEDIUM / 0
| Ecosystem | Package | Affected range | First patched |
|---|---|---|---|
| npm | msgpack5 | < 6.1.0 | 6.1.0 |
Original records & references
PUBLISHED 2026-10-08T13:17:15-04:00
MODIFIED 2026-10-09T12:17:22-04:00
INGESTED 2026-10-10T20:55:03-04:00