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CVE-2026-107299— msgpack5: Reserved byte can cause unbounded stream buffering

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 6.1.0 版本之前，流式解码器将保留的 MessagePack 字节 0xc1 视为不完整的输入，而不是无效的输入。当 0xc1 出现在数据流开头时，后续数据会被持续缓冲，而解码器则在等待无法使该值变为合法的字节。这可能导致远程对等方通过耗尽内存来发起拒绝服务攻击。此问题已在 6.1.0 版本中得到修复。

CVSS 5.9 · Medium

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 1

VendorProduct Version RangeStatus
mcollina msgpack5 < 6.1.0 affected
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I. Basic Information for CVE-2026-107299

Vulnerability Information
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Vulnerability Title
msgpack5: Reserved byte can cause unbounded stream buffering
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, 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
语法无效结构处理不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
mcollina msgpack5 < 6.1.0 -

II. Public POCs for CVE-2026-107299

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III. Intelligence Information for CVE-2026-107299

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Other References for CVE-2026-107299 (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-2026-107298 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-228

V. Comments for CVE-2026-107299

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