AIKIDO-2026-581554
ujson is vulnerable to Memory Leak
37
Low Risk
This Affects:
ujsonTL;DR
ujson's C encoder calls a user supplied default handler to convert objects it cannot serialize directly. When that handler keeps returning values it also cannot serialize, the encoder recurses to its depth limit and raises a TypeError without releasing the last object the handler returned. Each failed ujson.dumps() call leaks that object, so repeated serialization of such inputs grows process memory. The fix drops the outstanding reference on the encoder's error path.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and you serialize objects with a custom default handler.
Background info
ujson is vulnerable to Memory Leak in versions 4.2.0 - 5.13.0.
How to fix this
Upgrade the ujson and/or the ultrajson library to the patch version.
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