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CVE-2026-92707— MessagePack: Nested arrays can blow past buffer length limits

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.

C版本的 MessagePack 是一个用于 C的 MessagePack 序列化库。在版本 2.5.303 和 3.1.9 之前，通过 PrimitiveObjectFormatter 将攻击者控制的 MessagePack 数据反序列化为 System.Object 类型时，可能导致过度的内存分配。该格式化器在达到配置的图深度限制并拒绝输入之前，会预先根据每个声明的数组长度分配一个 object[] 对象。而嵌套的数组头部可以利用相同的尾部未读取字节来满足各头部的长度验证要求。因此，即使是一个相对较小的有效负载

CVSS 5.3 · Medium

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 2

VendorProduct Version RangeStatus
MessagePack-CSharp MessagePack-CSharp < 2.5.303 affected
>= 3.0.0, < 3.1.9 affected
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I. Basic Information for CVE-2026-92707

Vulnerability Information
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Vulnerability Title
MessagePack: Nested arrays can blow past buffer length limits
Source: CVE Program / CVE List V5
Vulnerability Description
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.303 and 3.1.9, deserializing attacker-controlled MessagePack data as System.Object through PrimitiveObjectFormatter can cause excessive memory allocation. The formatter allocates an object[] from each declared array length before the configured object-graph depth limit rejects the input, while nested array headers can reuse the same trailing unread bytes to satisfy per-header length validation. A comparatively small payload can therefore keep many large arrays alive at once. When an attacker can submit such data repeatedly, the allocations can cause severe managed-heap pressure, excessive garbage collection, process termination, or loss of service. Exposure requires an application to deserialize untrusted data through the affected formatter path and permit repeated attacker-controlled submissions, such as a reachable ASP.NET Core SignalR hub method with an object parameter and AddMessagePackProtocol() enabled. This issue is fixed in versions 2.5.303 and 3.1.9.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1325
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
MessagePack-CSharp MessagePack-CSharp < 2.5.303 -

II. Public POCs for CVE-2026-92707

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III. Intelligence Information for CVE-2026-92707

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Patches & Fixes for CVE-2026-92707 (1)

Vendor Advisories for CVE-2026-92707 (1)

Vendor Pages for CVE-2026-92707 (2)

IV. Related Vulnerabilities

Same product: MessagePack-CSharp
Same vendor: MessagePack-CSharp
Same weakness: CWE-1325

V. Comments for CVE-2026-92707

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