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CVE-2026-107301— msgpack5: Partial options disable prototype protection

Quick assessment

Affected
mcollina msgpack5
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

msgpack5 是一个适用于 Node.js 和浏览器的 MessagePack v5 实现。在版本 6.1.0 之前，如果使用空或部分初始化的 options 对象构造 msgpack5 实例，将禁用默认的 protoAction: 'error' 保护机制。此时，若解码得到的消息包中包含一个 __proto__ 键，该键可能导致解码对象的 prototype 被替换，从而可能改变其继承的属性或影响下游行为（尽管不会全局修改 Object.prototype）。该问题已在版本 6.1.0 中得到修复。

CVSS 6.5 · Medium

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
mcollina msgpack5 < 6.1.0 affected
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I. Basic Information for CVE-2026-107301

Vulnerability Information
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Vulnerability Title
msgpack5: Partial options disable prototype protection
Source: CVE Program / CVE List V5
Vulnerability Description
msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, constructing msgpack5 with an empty or partial options object disables the default protoAction: 'error' protection. A decoded map containing a __proto__ key can then replace the decoded object's prototype, potentially changing inherited properties or downstream behavior, although Object.prototype is not modified globally. This issue is fixed in version 6.1.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1321
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
mcollina msgpack5 < 6.1.0 -

II. Public POCs for CVE-2026-107301

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III. Intelligence Information for CVE-2026-107301

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Other References for CVE-2026-107301 (3)

Same Patch Batch · mcollina · 2026-10-08 · 7 CVEs total

CVE-2026-107300 7.5 HIGH msgpack5: Many buffered values can exhaust the streaming decoder stack
CVE-2026-107302 7.5 HIGH msgpack5: Truncated map32 headers throw an unexpected error
CVE-2026-107297 5.9 MEDIUM msgpack5: Quadratic parsing in the streaming decoder
CVE-2026-107299 5.9 MEDIUM msgpack5: Reserved byte can cause unbounded stream buffering
CVE-2026-107298 5.3 MEDIUM msgpack5: Deeply nested input can exhaust the decoder stack
CVE-2026-107296 3.7 LOW msgpack5: Decoding negative int64 values mutates the input buffer

IV. Related Vulnerabilities

Same product: msgpack5
Same vendor: mcollina
Same weakness: CWE-1321

V. Comments for CVE-2026-107301

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