CVE-2025-4516Public exploit

Interpreter crash via stale unicode-escape data pointer

Published May 15, 2025 · Updated Jul 31, 2026

Use-after-free in CPython's unicode_escape decoder allows local users to crash an affected interpreter with crafted bytes. When a non-strict error handler runs, a temporary bytes object replaces the original input and invalidates the decoder's data pointer before later reads. The path requires unicode_escape decoding with ignore or replace error handling; ordinary decoding is unaffected.

CVSS severity5.9
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in CPython's unicode_escape decoder allows local users to crash an affected interpreter with crafted bytes. When a non-strict error handler runs, a temporary bytes object replaces the original input and invalidates the decoder's data pointer before later reads. The path requires unicode_escape decoding with ignore or replace error handling; ordinary decoding is unaffected.

The record

CVE
CVE-2025-4516
Published
May 15, 2025
Updated
Jul 31, 2026
Vendor
Python Software Foundation
Product
CPython
Classifications
CWE-416, T1499
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 15, 2025CVE publishedPublication date reported by the CVE source.
  2. Jul 31, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.9.23
  2. Affected versionversion=3.10.0 <3.10.18
  3. Affected versionversion=3.11.0 <3.11.13
  4. Affected versionversion=3.12.0 <3.12.11
  5. Affected versionversion=3.13.0 <3.13.4
  6. Affected versionversion=3.14.0a1 <3.14.0b2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Python Software Foundation · CPythonversion=0 <3.9.23; version=3.10.0 <3.10.18; version=3.11.0 <3.11.13; version=3.12.0 <3.12.11; version=3.13.0 <3.13.4; version=3.14.0a1 <3.14.0b2

Published CVSS scores

5.9National Vulnerability DatabaseCVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
5.1Oracle LinuxCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
5.9UbuntuCVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
6.2Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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