CVE-2025-4516
What it is
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.
At a glance
- Exploitability
- Can be exploited locally on the machine without logging in. High risk of service disruption.
- Exploit odds
- 0.2% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.2% in the next 30 days (EPSS).
- Severity: 5.9 MEDIUM (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.2% · EPSS, next 30 days
- Weakness
- CWE-416 · Use after free
- Record status
- Deferred
Attack profile CVSS 4.0 · 5.9
- Attack vector
- Local
- Complexity
- High
- Attack requirements
- Present
- Privileges needed
- None
- User interaction
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Raw 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
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2025-4516.md and follow it. Check whether this project is affected by CVE-2025-4516. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- https://github.com/python/cpython/commit/4398b788ffc1f954a2c552da285477d42a571292
- https://github.com/python/cpython/commit/6279eb8c076d89d3739a6edb393e43c7929b429d
- https://github.com/python/cpython/commit/69b4387f78f413e8c47572a85b3478c47eba8142
- https://github.com/python/cpython/commit/73b3040f592436385007918887b7e2132aa8431f
- https://github.com/python/cpython/commit/8d35fd1b34935221aff23a1ab69a429dd156be77
- https://github.com/python/cpython/commit/9f69a58623bd01349a18ba0c7a9cb1dad6a51e8e
- https://github.com/python/cpython/commit/ab9893c40609935e0d40a6d2a7307ea51aec598b
- https://github.com/python/cpython/pull/129648
References
- https://github.com/python/cpython/commit/4398b788ffc1f954a2c552da285477d42a571292
- https://github.com/python/cpython/commit/6279eb8c076d89d3739a6edb393e43c7929b429d
- https://github.com/python/cpython/commit/69b4387f78f413e8c47572a85b3478c47eba8142
- https://github.com/python/cpython/commit/73b3040f592436385007918887b7e2132aa8431f
- https://github.com/python/cpython/commit/8d35fd1b34935221aff23a1ab69a429dd156be77
- https://github.com/python/cpython/commit/9f69a58623bd01349a18ba0c7a9cb1dad6a51e8e
- https://github.com/python/cpython/commit/ab9893c40609935e0d40a6d2a7307ea51aec598b
- https://github.com/python/cpython/issues/133767
- https://github.com/python/cpython/pull/129648
- https://mail.python.org/archives/list/[email protected]/thread/L75IPBBTSCYEF56I2M4KIW353BB3AY74/
- http://www.openwall.com/lists/oss-security/2025/05/16/4
- http://www.openwall.com/lists/oss-security/2025/05/19/1