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CVE-2026-48513— MessagePack-CSharp: DynamicUnionResolver generated deserializers miss depth enforcement

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DynamicUnionResolver发出的运行时生成的union反序列化器没有调用MessagePackSecurity.DepthStep且未递减递归反序列化和跳过路径的Depth，导致union反序列化未一致参与最大对象图深度强制执行，可能允许攻击者

AI Predicted 7.5 Difficulty: Moderate 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-2026-48513

Vulnerability Information
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Vulnerability Title
MessagePack-CSharp: DynamicUnionResolver generated deserializers miss depth enforcement
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, runtime-generated union deserializers emitted by DynamicUnionResolver do not call MessagePackSecurity.DepthStep(ref reader) and do not decrement reader.Depth around recursive deserialization and skip paths. This means union deserialization does not consistently participate in the maximum object graph depth enforcement that protects other recursive formatter paths. For unknown union keys, the emitted deserializer calls reader.Skip() on attacker-controlled data without an enclosing depth step. 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
未经控制的递归
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DynamicUnionResolver发出的运行时生成的union反序列化器没有调用MessagePackSecurity.DepthStep且未递减递归反序列化和跳过路径的Depth，导致union反序列化未一致参与最大对象图深度强制执行，可能允许攻击者
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-2026-48513

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III. Intelligence Information for CVE-2026-48513

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Vendor Advisories for CVE-2026-48513 (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-2026-48512 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-2026-48510 MessagePack-CSharp: LZ4 decompression allocates from unbounded declared output lengths
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-674

V. Comments for CVE-2026-48513

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