CVE-2026-12003

Local privilege escalation via source-tree landmark hijack

Published Jun 16, 2026 · Updated Jun 16, 2026

Uncontrolled search path in affected CPython releases allows local users to gain elevated code execution on Windows. When pybuilddir.txt is absent, getpath.py treats ....\Modules\Setup.local as a source-tree landmark and adds a sibling Lib directory to sys.path without checking whether low-privilege users can write there. Exploitation requires a writable directory two levels above a legacy all-users installation and execution by a more privileged user; per-user installs with equivalent parent-directory permissions are not exposed.

CVSS severity5.3
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled search path in affected CPython releases allows local users to gain elevated code execution on Windows. When pybuilddir.txt is absent, getpath.py treats ....\Modules\Setup.local as a source-tree landmark and adds a sibling Lib directory to sys.path without checking whether low-privilege users can write there. Exploitation requires a writable directory two levels above a legacy all-users installation and execution by a more privileged user; per-user installs with equivalent parent-directory permissions are not exposed.

The record

CVE
CVE-2026-12003
Published
Jun 16, 2026
Updated
Jun 16, 2026
Vendor
Python Software Foundation
Product
CPython
Classifications
CWE-427, T1574
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=0 <3.15.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Python Software Foundation · CPythonversion=0 <3.15.0

Published CVSS scores

5.3Python Software FoundationCVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-427Uncontrolled Search Path Element
T1574Hijack Execution Flow

Public exploit references

No public exploit references are available in this record.

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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