MessagePack-CSharp: Multi-dimensional array formatters allocate from unchecked dimensions_CVE-2026-48515

6.3 / 10

MEDIUM

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

Description

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePack-CSharp's multi-dimensional array formatters read dimension lengths directly from the payload and allocate T[,], T[,,], or T[,,,] before validating that the dimension product matches the encoded element count. The formatter reads a guarded element array header, but allocation of the target multi-dimensional array happens before the dimensions are checked against that element count. A small payload can therefore declare large dimensions, provide an empty or tiny inner array, and cause a large heap allocation before element data is validated. This vulnerability is fixed in 2.5.301 and 3.1.7.

Basic Information

ID CVE-2026-48515

Source GitHub_M

Published Jun 22, 2026 at 21:10

Affected Product

Vendor MessagePack-CSharp

Product MessagePack-CSharp

Version >= 3.1.7, < 3.1.7

Affected Versions MessagePack-CSharp MessagePack-CSharp >= 3.1.7, < 3.1.7
MessagePack-CSharp MessagePack-CSharp < 2.5.301

CWE Classification

CWE-770

References

github.com /MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-cxmj-83gh-fp49

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