Vulnerability · Published Jun 22, 2026 · Assigned by GitHub_M
CVE-2026-48506MessagePack-CSharp: MessagePackReader.Skip can recurse without enforcing maximum object graph depth
High 7.5
In plain English
A high-severity security flaw in MessagePack-CSharp from MessagePack-CSharp. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePackReader.TrySkip() recursively descends into nested arrays and maps without incrementing the reader depth or calling the configured depth checks. This bypasses MessagePackSecurity.MaximumObjectGraphDepth, the library's documented protection against deeply nested object graphs. Many generated and dynamic formatters call reader.Skip() when they encounter unknown map keys, unknown array members, ignored fields, or data that should be skipped for forward compatibility. A deeply nested value in one of these skipped positions can therefore cause unbounded recursion and an uncatchable StackOverflowException. This vulnerability is fixed in 2.5.301 and 3.1.7.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| NuGet | messagepack | 2.5.301 | GHSA-vh6j-jc39-fggf |
| NuGet | messagepack | 3.1.7 | GHSA-vh6j-jc39-fggf |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| MessagePack-CSharp | MessagePack-CSharp | >= 3.1.7, < 3.1.7< 2.5.301 |
Weakness: CWE-674 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H