Microsoft security update for CVE-2026-48509 — azl3 python-msgpack 1.2.3-1 on Azure Linux 3.0
🔗 CVE IDs covered (1)
📋 Microsoft's advisory
EchelonGraph does not copy Microsoft's advisory page: its FAQ and remediation text are not shown here. Read the advisory on https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-48509. This page also shows what EchelonGraph holds for CVE-2026-48509, with the description from its CVE record, which the CVE Numbering Authority that assigned the CVE wrote: for a CVE Microsoft assigned, often in the words of Microsoft's own advisory.
🎯 Affected products1
- azl3 python-msgpack 1.2.3-1 on Azure Linux 3.0
✅ Updates Microsoft lists: 1 update
1 row: one per KB article or update, update type and fixed build. Their details are on Microsoft's advisory.
| KB article | Update | Fixed build |
|---|---|---|
| — | Security Update | — |
🧭 EchelonGraph on CVE-2026-48509
- EchelonGraph score
- 9.1 CRITICAL
- CISA KEV
- Not listed
- Fix status
- A fix is available — apply it.
Description from the CVE record (CVE.org), as published by its numbering authority
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, the parameterless MessagePackInputFormatter() constructor uses default serializer options, which resolve to MessagePackSerializerOptions.Standard with MessagePackSecurity.TrustedData. The formatter is designed for ASP.NET Core MVC request bodies, which commonly cross an HTTP trust boundary. This insecure default can expose applications to denial-of-service attacks that MessagePackSecurity.UntrustedData is intended to mitigate, such as hash-collision attacks against dictionary-like model properties. This vulnerability is fixed in 2.5.301 and 3.1.7.
Published by GitHub, Inc., the CVE Numbering Authority that assigned CVE-2026-48509, in its CVE record at CVE.org; reused under the CVE Program's Terms of Use (its licence and MITRE's copyright notice are in our Terms of Service).