CVE-2025-4516

Use-after-free in "unicode_escape" decoder with error handler

Description

There is an issue in CPython when using bytes.decode("unicode_escape", error="ignore|replace"). 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 DecodeError.

Patch Available

Fix available through Seal Security.  
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Fix without upgrading

Score

5.9

Severity

Medium

Ecosystem

APT

Publish Date

May 15, 2025

Modified Date

October 8, 2025

Score Vector

CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected Versions