Bug 1256686 (CVE-2015-5224)

Summary: CVE-2015-5224 util-linux: File name collision due to incorrect mkstemp use
Product: [Other] Security Response Reporter: Adam Mariš <amaris>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED NOTABUG QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: jonathan, kzak
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2015-09-02 12:03:36 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On: 1256751    
Bug Blocks: 1256689    

Description Adam Mariš 2015-08-25 09:27:24 UTC
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, O_RDWR|O_CREAT|O_EXCL|O_CLOEXEC);
where localtmp is "/etc/%s.XXXXXX" and %s is __progname (i.e., argv[0]'s

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

Upstream patch:

Comment 1 Adam Mariš 2015-08-25 12:02:39 UTC
Created util-linux tracking bugs for this issue:

Affects: fedora-all [bug 1256751]

Comment 2 Stefan Cornelius 2015-09-02 12:03:36 UTC
We're not affected. Our binaries do not use the mkostemp function.


This issue did not affect the versions of util-linux as shipped with Red Hat Enterprise Linux 5 and 7. This issue does not affect the versions of util-linux-ng as shipped with Red Hat Enterprise Linux 6.