CVE-2025-4516
CVE-2025-4516 is a medium-severity vulnerability with a CVSS 4.0 base score of 5.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-416.
Key facts
- Severity: Medium (CVSS 4.0 base score 5.9)
- EPSS exploit prediction: 0% (7th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2025-15156
- Weakness: CWE-416
- Published:
- Last modified:
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.
Frequently asked questions
- What is CVE-2025-4516?
- 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.
- How severe is CVE-2025-4516?
- CVE-2025-4516 has a CVSS 4.0 base score of 5.9, rated medium severity.
- Is CVE-2025-4516 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (7th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2025-4516?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- Does CVE-2025-4516 have an EU (EUVD) identifier?
- Yes. CVE-2025-4516 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-15156.
- When was CVE-2025-4516 published?
- CVE-2025-4516 was published on 2025-05-15 and last updated on 2026-06-17.
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
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