There is a MEDIUM severity security issue in CPython when using bytes.decode("unicode_escape", error="ignore|replace"). The use-after-free being exploited would likely result in a crash.

If you are not using the "unicode_escape" encoding or an error handler your usage is not affected. To work-around this issue you may stop using the error= handler and instead wrap the bytes.decode() call in a try-except catching the decoding error.

Please see the linked CVE ID for the latest information on affected versions:

• https://www.cve.org/CVERecord?id=CVE-2025-4516
• https://github.com/python/cpython/pull/129648