Cython: To allow builds of Python to be run from an in-tree layout (rather than an installed file layout), the VPATH
Affects cythonSource GCVE Database
Not known to be exploited · CVSS 5.3 Medium.
Data as of 9 Nov 2026, 14:21 UTC
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 16 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.10cythonpkg:deb/ubuntu/cython?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 25.10cythonpkg:deb/ubuntu/cython?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 20.04 LTScythonpkg:deb/ubuntu/cython?arch=source&distro=focalOther threats | Affected
| Fixed in– |
Ubuntu 18.04 LTScythonpkg:deb/ubuntu/cython?arch=source&distro=bionicOther threats | Affected
| Fixed in– |
Ubuntu 16.04 LTScythonpkg:deb/ubuntu/cython?arch=source&distro=xenialOther threats | Affected
| Fixed in– |
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AI-suggested
The vendor recommends migrating away from legacy all-user installers on Windows to the new Python install manager, which installs per-user and mitigates this risk. Alternative mitigations include preemptively creating and restricting access to the 'Modules' directory two levels above the Python install directory. Future Python releases will remove the fallback landmark detection, so ensuring the presence of the 'pybuilddir.txt' file is also a mitigation path.
Description
A vulnerability in Python's build system on Windows allows low-privilege users to potentially escalate privileges by creating a landmark file and alternative library folder outside the Python install directory. This occurs due to the VPATH variable pointing to a directory with weaker permissions in legacy all-user installations. The issue affects certain legacy installers and is mitigated by using the new Python install manager or restricting access to specific directories. Future Python releases will remove the fallback landmark detection that enables this behavior.