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CVE-2026-107296— msgpack5: Decoding negative int64 values mutates the input buffer

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 是适用于 Node.js 和浏览器的 MessagePack v5 实现。在版本 6.1.0 之前，当解码负号 64 位有符号整数时，会在计算其值的过程中修改调用者提供的输入缓冲区中对应的字节。对于保留或重用编码输入数据进行完整性检查、日志记录或后续处理的应用程序，可能会观察到静默损坏的数据；而正整数和其他 MessagePack 数据类型不受此问题影响。该问题已在版本 6.1.0 中修复。

CVSS 3.7 · Low

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-2026-107296

Vulnerability Information
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Vulnerability Title
msgpack5: Decoding negative int64 values mutates the input buffer
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, decoding a negative signed 64-bit integer modifies the corresponding bytes in the caller-provided input buffer while computing the value. Applications that retain or reuse encoded input for integrity checks, logging, or later processing can observe silently corrupted data, while positive integers and other MessagePack value types are unaffected. 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:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对假设不可变数据的修改(MAID)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
mcollina msgpack5 < 6.1.0 -

II. Public POCs for CVE-2026-107296

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III. Intelligence Information for CVE-2026-107296

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Other References for CVE-2026-107296 (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-2026-107301 6.5 MEDIUM msgpack5: Partial options disable prototype protection
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

IV. Related Vulnerabilities

Same product: msgpack5
Same vendor: mcollina
Same weakness: CWE-471

V. Comments for CVE-2026-107296

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