CVE-2026-107299 Details
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.
A memory exhaustion vulnerability has been identified in msgpack5, a MessagePack v5 implementation for Node.js and the browser, in versions prior to 6.1.0. The issue arises because the streaming decoder incorrectly treats the reserved MessagePack byte 0xc1 as incomplete input rather than invalid. When 0xc1 is at the beginning of a stream, the decoder buffers subsequent data while waiting for bytes that can never validate the value, allowing a remote peer to exhaust memory. This vulnerability has been addressed in version 6.1.0.
Users can update to msgpack5 version 6.1.0 or later, where this vulnerability has been fixed. For those unable to upgrade, it is recommended to manually reject the reserved byte 0xc1 before streaming input to msgpack5 and to enforce byte and time limits on the stream.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Oct 8, 2026CISA-ADP
Assessed Oct 8, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/mcollina/msgpack5/commit/85da345bf1acc18ca441741e5cf4aa0ed0d69314 | [email protected] | Source CodeVendor |
| https://github.com/mcollina/msgpack5/releases/tag/v6.1.0 | [email protected] | Release NotesVendor |
| https://github.com/mcollina/msgpack5/security/advisories/GHSA-26wq-p25c-j6fv | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-228 | Improper Handling of Syntactically Invalid Structure | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| mcollina msgpack5 | < 6.1.0 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Oct 9, 2026 | CVE Modified | CISA-ADP |
| Oct 8, 2026 | New CVE Received | [email protected] |