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CVE-2026-48109— MessagePack-CSharp: LZ4 decompression may fail with AccessViolationException after dereferencing memory from bad input

CVSS 8.2 · High EPSS 0.51% · P41

Affected Version Matrix 2

VendorProductVersion RangeStatus
MessagePack-CSharpMessagePack-CSharp>= 3.1.7, < 3.1.7affected
< 2.5.301affected
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I. Basic Information for CVE-2026-48109

Vulnerability Information
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Vulnerability Title
MessagePack-CSharp: LZ4 decompression may fail with AccessViolationException after dereferencing memory from bad input
Source: CVE Program / CVE List V5
Vulnerability Description
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an AccessViolationException during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This vulnerability is fixed in 2.5.301 and 3.1.7.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
MessagePack-CSharp 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
MessagePack-CSharp MessagePack-CSharp是MessagePack-CSharp团队的一款消息序列化工具。 MessagePack-CSharp 2.5.301之前版本和3.1.7之前版本存在输入验证错误漏洞，该漏洞源于LZ4解压缩路径中使用的解码器实现基于不检查源长度限制的已弃用快速解压缩算法，可能导致远程攻击者发送特制MessagePack有效载荷，操纵LZ4令牌/长度字段强制从压缩输入缓冲区越界读取，从而触发AccessViolationException导致进程终止
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

VendorProductAffected VersionsCPESubscribe
MessagePack-CSharpMessagePack-CSharp >= 3.1.7, < 3.1.7 -

II. Public POCs for CVE-2026-48109

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AI-Generated POCPremium
Qwen3.6-35B-A3B · 7669 chars
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III. Intelligence Information for CVE-2026-48109

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Vendor Advisories for CVE-2026-48109 (1)

Same Patch Batch · MessagePack-CSharp · 2026-06-22 · 12 CVEs total

CVE-2026-485067.5 HIGHMessagePack-CSharp: MessagePackReader.Skip can recurse without enforcing maximum object gr
CVE-2026-48516MessagePack-CSharp: InterfaceLookupFormatter bypasses collision-resistant comparer setting
CVE-2026-48511MessagePack-CSharp: ExpandoObject formatter can perform quadratic insertion work on untrus
CVE-2026-48513MessagePack-CSharp: DynamicUnionResolver generated deserializers miss depth enforcement
CVE-2026-48512MessagePack-CSharp: JSON conversion APIs can recurse without consistent depth enforcement
CVE-2026-48502MessagePack-CSharp: Denial of service vulnerabilities can swamp the CPU or crash the proce
CVE-2026-48509MessagePack-CSharp: ASP.NET Core MessagePackInputFormatter defaults to TrustedData for HTT
CVE-2026-48510MessagePack-CSharp: LZ4 decompression allocates from unbounded declared output lengths
CVE-2026-48517MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays
CVE-2026-48515MessagePack-CSharp: Multi-dimensional array formatters allocate from unchecked dimensions
CVE-2026-48514MessagePack-CSharp: Unity unsafe blit formatter allocates from unbounded byte length

IV. Related Vulnerabilities

Same product: MessagePack-CSharp
Same vendor: MessagePack-CSharp
Same weakness: CWE-20

V. Comments for CVE-2026-48109

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