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CVE-2026-48510— MessagePack-CSharp: LZ4 decompression allocates from unbounded declared output lengths

Quick assessment

Affected
MessagePack-CSharp MessagePack-CSharp
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.

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之前版本存在资源管理错误漏洞，该漏洞源于解压缩Lz4Block或Lz4BlockArray有效载荷时在验证压缩数据有效性前根据声明长度分配输出缓冲区，可能导致小型有效载荷声明极大未压缩长度并强制进行大内存分配。

AI Predicted 7.5 Difficulty: Easy EPSS 0.40% · P33

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 2

VendorProduct Version RangeStatus
MessagePack-CSharp MessagePack-CSharp >= 3.0, < 3.1.7 affected
< 2.5.301 affected
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I. Basic Information for CVE-2026-48510

Vulnerability Information
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Vulnerability Title
MessagePack-CSharp: LZ4 decompression allocates from unbounded declared output lengths
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, when MessagePack-CSharp decompresses Lz4Block or Lz4BlockArray payloads, it reads declared uncompressed lengths from the wire and allocates output buffers based on those lengths before validating that the compressed data is valid or that the declared expansion is reasonable. A small payload can claim a very large uncompressed length and force a large allocation before LZ4 decoding begins. This vulnerability is fixed in 2.5.301 and 3.1.7.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
对高度压缩数据的处理不恰当(数据放大攻击)
Source: CVE Program / CVE List V5
Vulnerability Title
MessagePack-CSharp 资源管理错误漏洞
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之前版本存在资源管理错误漏洞，该漏洞源于解压缩Lz4Block或Lz4BlockArray有效载荷时在验证压缩数据有效性前根据声明长度分配输出缓冲区，可能导致小型有效载荷声明极大未压缩长度并强制进行大内存分配。
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
MessagePack-CSharp MessagePack-CSharp >= 3.0, < 3.1.7 -

II. Public POCs for CVE-2026-48510

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III. Intelligence Information for CVE-2026-48510

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Vendor Advisories for CVE-2026-48510 (1)

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

CVE-2026-48109 8.2 HIGH MessagePack-CSharp: LZ4 decompression may fail with AccessViolationException after derefer
CVE-2026-48506 7.5 HIGH MessagePack-CSharp: MessagePackReader.Skip can recurse without enforcing maximum object gr
CVE-2026-48516 MessagePack-CSharp: InterfaceLookupFormatter bypasses collision-resistant comparer setting
CVE-2026-48511 MessagePack-CSharp: ExpandoObject formatter can perform quadratic insertion work on untrus
CVE-2026-48513 MessagePack-CSharp: DynamicUnionResolver generated deserializers miss depth enforcement
CVE-2026-48512 MessagePack-CSharp: JSON conversion APIs can recurse without consistent depth enforcement
CVE-2026-48502 MessagePack-CSharp: Denial of service vulnerabilities can swamp the CPU or crash the proce
CVE-2026-48509 MessagePack-CSharp: ASP.NET Core MessagePackInputFormatter defaults to TrustedData for HTT
CVE-2026-48517 MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays
CVE-2026-48515 MessagePack-CSharp: Multi-dimensional array formatters allocate from unchecked dimensions
CVE-2026-48514 MessagePack-CSharp: Unity unsafe blit formatter allocates from unbounded byte length

IV. Related Vulnerabilities

Same product: MessagePack-CSharp
Same vendor: MessagePack-CSharp
Same weakness: CWE-409

V. Comments for CVE-2026-48510

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