Use After Free Affecting msgpack package, versions [,1.2.1)
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Test your applications- Snyk IDSNYK-PYTHON-MSGPACK-17391445
- published21 Jun 2026
- disclosed19 Jun 2026
- creditUnknown
Introduced: 19 Jun 2026
New CVE NOT AVAILABLE CWE-416 (opens in a new tab)Common Weakness Enumeration (CWE) is a category system for software weaknesses
How to fix?
Upgrade msgpack to version 1.2.1 or higher.
Overview
msgpack is an efficient binary serialization format.
Affected versions of this package are vulnerable to Use After Free in the unpacker' when it is reused after an error has occurred. An attacker can cause a crash or denial of service by repeatedly triggering errors and reusing the same unpacker` instance with untrusted input.
Workaround
This vulnerability can be mitigated by creating a new unpacker instance instead of reusing one after an error, and by discarding the Stream and Streaming Unpacker if an error occurs during streaming unpacking.