Description
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.
Published: 2026-10-08
Score: 5.9 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-26wq-p25c-j6fv msgpack5: Reserved byte can cause unbounded stream buffering
History

Fri, 09 Oct 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 09 Oct 2026 09:15:00 +0000

Type Values Removed Values Added
First Time appeared Mcollina
Mcollina msgpack5
Vendors & Products Mcollina
Mcollina msgpack5

Thu, 08 Oct 2026 17:15:00 +0000

Type Values Removed Values Added
Description 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.
Title msgpack5: Reserved byte can cause unbounded stream buffering
Weaknesses CWE-228
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Subscriptions

Mcollina Msgpack5
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-09T15:15:00.980Z

Reserved: 2026-10-07T15:53:23.587Z

Link: CVE-2026-107299

cve-icon Vulnrichment

Updated: 2026-10-08T20:23:18.497Z

cve-icon NVD

Status : Deferred

Published: 2026-10-08T17:17:15.850

Modified: 2026-10-09T16:17:22.147

Link: CVE-2026-107299

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-09T08:04:12Z

Weaknesses
  • CWE-228

    Improper Handling of Syntactically Invalid Structure