Bug 605397 (CVE-2010-2431)

Summary: CVE-2010-2431 cups: latent privilege escalation vulnerability
Product: [Other] Security Response Reporter: Vincent Danen <vdanen>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: jlieskov, jpopelka, jrusnack, twaugh, ykopkova
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2010-10-29 07:36:56 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: 604728, 605399, 646767, 646768    
Bug Blocks:    

Description Vincent Danen 2010-06-17 20:27:36 UTC
Quoting from the upstream bug report http://cups.org/str.php?L3510:

directory that is writable by unprivileged processes.

This is a latent privilege escalation vulnerability.  It can be
exploited only in the presence of other CUPS vulnerabilities.

Why this is privilege escalation
--------------------------------

This is privilege escalation, because an unprivileged process can
trick the CUPS server into overwriting arbitrary files as root.

Example:

    drwxrwxr-x  4 root lp /var/cache/cups
    -rw-r-----  1 root lp /var/cache/cups/remote.cache

This file is opened with cupsFileOpen() which simply opens the file
with open(filename, O_WRONLY | O_TRUNC | O_CREAT | O_LARGEFILE |
O_BINARY, 0666).

If a CUPS "external" program has a vulnerability, an attacker can
use the group=lp privileges to replace /var/cache/cups/remote.cache
with a symlink to a root-writable file. CUPS will then overwrite
that file as root. A similar latent vulnerability exists for the
state file /var/cache/cups/job.cache.

Why this is a latent vulnerability
----------------------------------

This is a latent vulnerability, because there is no known exploit
for CUPS "external" programs that run as user=lp, group=lp.


The upstream fix looks more like a preventative fix as there does not seem to be anything exploitable here, so this looks like more a hardening than a response to an actual flaw.

Comment 2 Vincent Danen 2010-06-17 20:34:24 UTC
Created cups tracking bugs for this issue

Affects: fedora-all [bug 605399]

Comment 3 Fedora Update System 2010-06-18 11:03:24 UTC
cups-1.4.4-1.fc13 has been submitted as an update for Fedora 13.
http://admin.fedoraproject.org/updates/cups-1.4.4-1.fc13

Comment 4 Fedora Update System 2010-06-18 11:04:24 UTC
cups-1.4.4-1.fc12 has been submitted as an update for Fedora 12.
http://admin.fedoraproject.org/updates/cups-1.4.4-1.fc12

Comment 5 Fedora Update System 2010-06-18 11:05:00 UTC
cups-1.4.4-1.fc11 has been submitted as an update for Fedora 11.
http://admin.fedoraproject.org/updates/cups-1.4.4-1.fc11

Comment 6 Jan Lieskovsky 2010-06-23 10:33:32 UTC
Common Vulnerabilities and Exposures assigned an identifier CVE-2010-2431 to
this vulnerability:

The cupsFileOpen function in CUPS before 1.4.4 allows local users,
with lp group membership, to overwrite arbitrary files via a symlink
attack on the (1) /var/cache/cups/remote.cache or (2)
/var/cache/cups/job.cache file.

With references:
  [1] http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-2431
  [2] http://cups.org/articles.php?L596
  [3] http://cups.org/str.php?L3510

Comment 9 Fedora Update System 2010-06-24 12:22:33 UTC
cups-1.4.4-4.fc13 has been submitted as an update for Fedora 13.
http://admin.fedoraproject.org/updates/cups-1.4.4-4.fc13

Comment 10 Fedora Update System 2010-06-25 18:10:23 UTC
cups-1.4.4-4.fc11 has been pushed to the Fedora 11 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 11 Fedora Update System 2010-07-01 18:44:22 UTC
cups-1.4.4-5.fc13 has been pushed to the Fedora 13 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 12 Fedora Update System 2010-07-27 02:45:54 UTC
cups-1.4.4-5.fc12 has been pushed to the Fedora 12 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 16 errata-xmlrpc 2010-10-29 01:44:15 UTC
This issue has been addressed in following products:

  Red Hat Enterprise Linux 5

Via RHSA-2010:0811 https://rhn.redhat.com/errata/RHSA-2010-0811.html

Comment 17 Vincent Danen 2010-10-29 02:58:02 UTC
Statement:

This issue did not affect the versions of CUPS as shipped with Red Hat Enterprise Linux 3 or 4.  It was addressed in Red Hat Enterprise Linux 5 via RHSA-2010:0811.