Bug 1233043 (CVE-2015-3245) - CVE-2015-3245 libuser: does not filter newline characters in the GECOS field
Summary: CVE-2015-3245 libuser: does not filter newline characters in the GECOS field
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2015-3245
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1235517 1235518 1235519 1235520 1246225
Blocks: 1233055
TreeView+ depends on / blocked
 
Reported: 2015-06-18 06:50 UTC by Huzaifa S. Sidhpurwala
Modified: 2021-09-13 09:20 UTC (History)
6 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
It was found that libuser, as used by the chfn userhelper functionality, did not properly filter out newline characters in GECOS fields. A local, authenticated user could use this flaw to corrupt the /etc/passwd file, resulting in a denial-of-service on the system.
Clone Of:
Environment:
Last Closed: 2015-07-29 07:17:38 UTC


Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2015:1482 0 normal SHIPPED_LIVE Important: libuser security update 2015-07-23 21:59:57 UTC
Red Hat Product Errata RHSA-2015:1483 0 normal SHIPPED_LIVE Important: libuser security update 2015-07-24 00:44:52 UTC

Description Huzaifa S. Sidhpurwala 2015-06-18 06:50:27 UTC
It was found that libuser, as used in the chfn userhelper functionality, does not properly filter out newline characters, which allows an authenticated local attacker to corrupt the /etc/passwd file and cause denial-of-service against the system.

Acknowledgements:

Red Hat would like to thank Qualys for reporting this issue.

Comment 4 Florian Weimer 2015-07-23 12:09:28 UTC
This vulnerability is addressed by additional checks on GECOS field contents within the libuser library, and not in the userhelper program in the usermode package.  This change will also protect other applications which use libuser.

Comment 5 Florian Weimer 2015-07-23 12:56:38 UTC
Mitigation:

Add pam_warn and pam_deny rules to /etc/pam.d/chfn and /etc/pam.d/chsh to prevent non-root users from using this functionality.  With these edits, the files should contain:

#%PAM-1.0
auth       sufficient   pam_rootok.so
auth required pam_warn.so
auth required pam_deny.so
auth       include      system-auth
account    include      system-auth
password   include      system-auth
session    include      system-auth

Afterwards, attempts by unprivileged users to use chfn and chsh (and the respective functionality in the userhelper program) will fail, and will be logged (by default in /var/log/secure).

Comment 6 Martin Prpič 2015-07-23 12:57:37 UTC
External References:

https://access.redhat.com/articles/1537873

Comment 7 errata-xmlrpc 2015-07-23 18:01:48 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6

Via RHSA-2015:1482 https://rhn.redhat.com/errata/RHSA-2015-1482.html

Comment 8 Florian Weimer 2015-07-23 18:11:58 UTC
Created libuser tracking bugs for this issue:

Affects: fedora-all [bug 1246225]

Comment 9 errata-xmlrpc 2015-07-23 20:45:33 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2015:1483 https://rhn.redhat.com/errata/RHSA-2015-1483.html

Comment 10 Florian Weimer 2015-07-29 07:07:09 UTC
Statement:

Red Hat Enterprise Linux 5 is now in Production 3 Phase of the support and maintenance life cycle. This vulnerability has been rated as having Moderate security impact and is not currently planned to be addressed in future updates. For additional information, refer to the Red Hat Enterprise Linux Life Cycle: https://access.redhat.com/support/policy/updates/errata/.

Comment 11 Fedora Update System 2015-07-30 13:55:12 UTC
libuser-0.62-1.fc22 has been pushed to the Fedora 22 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 12 Fedora Update System 2015-08-03 04:30:50 UTC
libuser-0.62-1.fc21 has been pushed to the Fedora 21 stable repository.  If problems still persist, please make note of it in this bug report.


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