PYSEC-2026-1056

vendorUSosv

Potential double free of buffer during string decoding

view advisory published 2026-07-06Licence: CC-BY-4.0

### Impact _What kind of vulnerability is it? Who is impacted?_ When an error occurs while reallocating the buffer for string decoding, the buffer gets freed twice. Due to how UltraJSON uses the internal decoder, this double free is impossible to trigger from Python. ### Patches _Has the problem been patched? What versions should users upgrade to?_ Users should upgrade to UltraJSON 5.4.0. ### Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading?_ There is no workaround. ### For more information If you have any questions or comments about this advisory: * Open an issue in [UltraJSON](http://github.com/ultrajson/ultrajson/issues)

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describes (1)

Related CVEs.

IDseverity exploitable
CVE-2022-31117USmedium5.9—
UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. In versions prior to 5.4.0 an error occurring while reallocating a buffer for string d…
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references

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