CVE-2026-48510
High
Description
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, when MessagePack-CSharp decompresses Lz4Block or Lz4BlockArray payloads, it reads declared uncompressed lengths from the wire and allocates output buffers based on those lengths before validating that the compressed data is valid or that the declared expansion is reasonable. A small payload can claim a very large uncompressed length and force a large allocation before LZ4 decoding begins. This vulnerability is fixed in 2.5.301 and 3.1.7.
SeverityHigh
CVSS7.5
Exploit probability—
ProductMessagepack
PublishedJun 22, 2026
First seenJun 22, 2026
How to fix
Update
- messagepack messagepack2.5.301, 3.1.7 or later
- MessagePack2.5.301, 3.1.7 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| messagepack messagepack | v < 2.5.301, 3.0.3 ≤ v < 3.1.7 | 2.5.301, 3.1.7 |
| MessagePackNuGet | v < 2.5.301, 3.0 ≤ v < 3.1.7 | 2.5.301, 3.1.7 |
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