AIKIDO-2026-342228
msgpack is vulnerable to Use-After-Free
48
Medium Risk
This Affects:
msgpackTL;DR
The unpackb() function copies non-contiguous input, such as a sliced memoryview, into a temporary contiguous buffer before parsing. When the input contains trailing bytes after a complete object, the trailing ExtraData payload is read from that temporary buffer after it has already been released, so the exception is built from freed memory. This can expose unrelated freed heap contents through the returned extra bytes or crash the interpreter. The fix copies the extra data out before the temporary buffer is released.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and you unpack untrusted or externally influenced data passed as a non-contiguous buffer such as a sliced memoryview that carries trailing bytes after a complete object.
Background info
msgpack is vulnerable to Use-After-Free in versions 0.5.0 - 1.2.1.
How to fix this
Upgrade the msgpack library to the patch version.
Are You Affected?
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