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CVE-2026-54522— MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure

Quick assessment

Affected
msgpack msgpack-ruby
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.

msgpack messagepack是msgpack团队开源的一种消息序列化格式。 MessagePack 1.8.2之前版本存在资源管理错误漏洞，该漏洞源于MessagePack::Buffer#clear函数在返回rmem页到共享池后未清除rmem_last、rmem_end和rmem_owner，导致后续Buffer#write和第二个MessagePack::Buffer可能别名该页并泄露或破坏跨缓冲区数据。

CVSS 2.1 · Low EPSS 0.23% · P12

Possible ATT&CK Techniques 1 AI

T1560.001 · Archive via Utility

Affected Version Matrix 1

VendorProduct Version RangeStatus
msgpack msgpack-ruby < 1.8.2 affected
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I. Basic Information for CVE-2026-54522

Vulnerability Information
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Vulnerability Title
MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure
Source: CVE Program / CVE List V5
Vulnerability Description
MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Buffer#clear in ext/msgpack/buffer.c leaves rmem_last, rmem_end, and rmem_owner stale after _msgpack_buffer_shift_chunk returns an rmem page to the shared pool, allowing a subsequent Buffer#write and a second MessagePack::Buffer to alias the page and disclose or corrupt cross-buffer data. This issue is fixed in version 1.8.2.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
释放后使用
Source: CVE Program / CVE List V5
Vulnerability Title
MessagePack 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
msgpack messagepack是msgpack团队开源的一种消息序列化格式。 MessagePack 1.8.2之前版本存在资源管理错误漏洞，该漏洞源于MessagePack::Buffer#clear函数在返回rmem页到共享池后未清除rmem_last、rmem_end和rmem_owner，导致后续Buffer#write和第二个MessagePack::Buffer可能别名该页并泄露或破坏跨缓冲区数据。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
msgpack msgpack-ruby < 1.8.2 -

II. Public POCs for CVE-2026-54522

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III. Intelligence Information for CVE-2026-54522

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Patches & Fixes for CVE-2026-54522 (1)

Vendor Advisories for CVE-2026-54522 (1)

IV. Related Vulnerabilities

Same vendor: msgpack
Same weakness: CWE-416

V. Comments for CVE-2026-54522

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