Race condition in the _get_masked_mode function in Lib/os.py in Python 3.2 through 3.5, when exist_ok is set to true and multiple threads are used, might allow local users to bypass intended file permissions by leveraging a separate application vulnerability before the umask has been set to the expected value.

References

• https://nvd.nist.gov/vuln/detail/CVE-2014-2667
• https://security.gentoo.org/glsa/201503-10
• http://bugs.python.org/issue21082
• http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00040.html
• http://lists.opensuse.org/opensuse-updates/2014-05/msg00007.html
• http://lists.opensuse.org/opensuse-updates/2014-05/msg00008.html
• http://www.openwall.com/lists/oss-security/2014/03/28/15
• http://www.openwall.com/lists/oss-security/2014/03/29/5
• http://www.openwall.com/lists/oss-security/2014/03/30/4