CVE-2026-107299

msgpack5: Reserved byte can cause unbounded stream buffering

Published Oct 8, 2026 CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

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
Type Values Removed Values Added
Metrics ssvc

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

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

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 9, 2026, 3:15 PM
Reserved
Oct 7, 2026, 3:53 PM
Status
Deferred
Published
Oct 8, 2026, 5:17 PM
Modified
Oct 9, 2026, 4:17 PM