CVE-2015-5224: Critical severity util-linux vulnerability
The following vulnerability in util-linux was announced (taken from http://seclists.org/oss-sec/2015/q3/423):
""" If the chfn and chsh binaries (both setuid-root) from util-linux/login-utils are compiled WITHOUT libuser support, they eventually call mkostemp(localtmp, ORDWR|OCREAT|OEXCL|OCLOEXEC); where localtmp is "/etc/%s.XXXXXX" and %s is progname (i.e., argv[0]'s basename).
An attacker could repeatedly execve chfn as "ld.so" until mkostemp() creates "/etc/ld.so.preload" (after a few days, in our tests). This particular example doesn't actually work, because "preload" is 7 chars and "XXXXXX" is 6 chars, but it seems there are other interesting possibilities, like "/etc/rc.status" and "/etc/krb5.keytab".
The impact of this vulnerability is probably very limited: most Linux distributions ship either the chfn/chsh binaries from the shadow-utils (NOT the login-utils ones), or the login-utils ones but WITH libuser support. """
Upstream patch: https://github.com/karelzak/util-linux/commit/bde91c85bdc77975155058276f99d2e0f5eab5a9
Other sources
The mkostemp function in login-utils in util-linux when used incorrectly allows remote attackers to cause file name collision and possibly other attacks.
— MITRE
Affected Software
Remediation
Patch Available
Event History
Frequently Asked Questions
What is the severity of CVE-2015-5224?
CVE-2015-5224 has a medium severity rating due to its potential for privilege escalation.
How do I fix CVE-2015-5224?
To fix CVE-2015-5224, upgrade util-linux to version 2.27 or later or ensure it is compiled with libuser support.
What are the affected versions of util-linux in CVE-2015-5224?
The affected versions include util-linux versions prior to 2.27 and 2.26.2 or lower.
What is the nature of the vulnerability in CVE-2015-5224?
CVE-2015-5224 is a privilege escalation vulnerability in the setuid-root binaries chfn and chsh when compiled without libuser support.
Can applications using util-linux be affected by CVE-2015-5224?
Yes, applications that rely on the vulnerable util-linux components can be exploited if they are compiled without appropriate protections.