MessagePack-CSharp MessagePack for C# up to 2.5.300/3.1.6 T[] allocation of resources

Summaryinfo

A vulnerability labeled as problematic has been found in MessagePack-CSharp MessagePack for C# up to 2.5.300/3.1.6. Affected is an unknown function. Executing a manipulation of the argument T[] can lead to allocation of resources. The identification of this vulnerability is CVE-2026-48514. The attack may be launched remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as problematic was found in MessagePack-CSharp MessagePack for C# up to 2.5.300/3.1.6. This vulnerability affects an unknown part. The manipulation of the argument T[] with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. As an impact it is known to affect availability. CVE summarizes:

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, UnsafeBlitFormatterBase.Deserialize reads an attacker-controlled byteLength from an extension payload and allocates an array based on that value before validating it against the extension header length or remaining payload bytes. The outer extension header is bounded by available input, but that bound is not used to constrain the inner byteLength before allocation. A very small payload can therefore request a very large T[] allocation. This vulnerability is fixed in 2.5.301 and 3.1.7.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-48514 since 05/21/2026. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 2.5.301 or 3.1.7 eliminates this vulnerability.

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Productinfo

Vendor

• MessagePack-CSharp

Name

• MessagePack for C#

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5.300
• 3.1.0
• 3.1.1
• 3.1.2
• 3.1.3
• 3.1.4
• 3.1.5
• 3.1.6

CPE 2.3info

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CPE 2.2info

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