CVE-2026-48515

MessagePack-CSharp: Multi-dimensional array formatters allocate from unchecked dimensions

Published Jun 22, 2026 CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Github GHSA Github GHSA GHSA-cxmj-83gh-fp49 MessagePack-CSharp: Multi-dimensional array formatters allocate from unchecked dimensions
History
Type Values Removed Values Added
First Time appeared Messagepack
Messagepack messagepack-csharp
Vendors & Products Messagepack
Messagepack messagepack-csharp
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title MessagePack-CSharp: Multi-dimensional array formatters allocate from unchecked dimensions
Weaknesses CWE-770
References
Metrics cvssV4_0

{'score': 6.3, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jun 25, 2026, 3:51 PM
Reserved
May 21, 2026, 4:18 PM
Status
Analyzed
Published
Jun 22, 2026, 10:16 PM
Modified
Jun 25, 2026, 5:16 PM