Vulnerability in Messagepack
CVE-2026-48506
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (38.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 38th percentile — 38.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000
Affected products
- Messagepack
- Messagepack-Csharp — versions >= 3.1.7, < 3.1.7, < 2.5.301
Weakness classification (CWE)
References
- github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-vh6j-… (Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-48506?
- CVE-2026-48506 is a high-severity vulnerability in Messagepack, classified under Uncontrolled Recursion. CVSS score: 7.5/10. Published 2026-06-22.
- How severe is CVE-2026-48506?
- High severity. CVSS v3 base score is 7.5 out of 10.