Common Desktop Environment 2.3.1 Buffer Overflow

2020.01.20
Credit: Marco Ivaldi
Risk: High
Local: Yes
Remote: No
CWE: CWE-119


CVSS Base Score: 7.2/10
Impact Subscore: 10/10
Exploitability Subscore: 3.9/10
Exploit range: Local
Attack complexity: Low
Authentication: No required
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

@Mediaservice.net Security Advisory #2020-02 (last updated on 2020-01-15) Title: Local privilege escalation via CDE dtsession Application: Common Desktop Environment 2.3.1 and earlier Common Desktop Environment 1.6 and earlier Platforms: Oracle Solaris 10 1/13 (Update 11) and earlier Other platforms are potentially affected (see below) Description: A local attacker can gain root privileges by exploiting a buffer overflow in CDE dtsession Author: Marco Ivaldi <marco.ivaldi@mediaservice.net> Vendor Status: Oracle <secalert_us@oracle.com> notified on 2019-11-13 CERT/CC notified on 2019-12-09 (tracking VU#308289) CVE Name: CVE-2020-2696 CVSS Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H (Base Score: 8.8) References: https://github.com/0xdea/advisories/blob/master/2020-02-cde-dtsession.txt https://www.oracle.com/security-alerts/cpujan2020.html https://sourceforge.net/p/cdesktopenv/wiki/Home/ https://www.oracle.com/technetwork/server-storage/solaris10/ https://www.mediaservice.net/ https://0xdeadbeef.info/ 1. Abstract A buffer overflow in the CheckMonitor() function in the Common Desktop Environment 2.3.1 and earlier and 1.6 and earlier, as distributed with Oracle Solaris 10 1/13 (Update 11) and earlier, allows local users to gain root privileges via a long palette name passed to dtsession in a malicious .Xdefaults file. Note that Oracle Solaris CDE is based on the original CDE 1.x train, which is different from the CDE 2.x codebase that was later open sourced. Most notably, the vulnerable buffer in the Oracle Solaris CDE is stack-based, while in the open source version it is heap-based. 2. Example Attack Session. bash-3.2$ cat /etc/release Oracle Solaris 10 1/13 s10x_u11wos_24a X86 Copyright (c) 1983, 2013, Oracle and/or its affiliates. All rights reserved. Assembled 17 January 2013 bash-3.2$ uname -a SunOS nostalgia 5.10 Generic_147148-26 i86pc i386 i86pc bash-3.2$ id uid=54322(raptor) gid=1(other) bash-3.2$ gcc raptor_dtsession_ipa.c -o raptor_dtsession_ipa -Wall bash-3.2$ ./raptor_dtsession_ipa 192.168.1.1:0 raptor_dtsession_ipa.c - CDE dtsession LPE for Solaris/Intel Copyright (c) 2019-2020 Marco Ivaldi <raptor@0xdeadbeef.info> Using SI_PLATFORM : i86pc (5.10) Using stack base : 0x8047fff Using rwx_mem address : 0xfeffa004 Using payload address : 0x8047dff Using strcpy() address : 0xfefe26a0 # id uid=0(root) gid=1(other) 3. Affected Platforms. All platforms shipping the Common Desktop Environment are potentially affected. This includes: * Oracle Solaris 10 1/13 (Update 11) and earlier [default installation] According to the CDE Wiki, the following platforms are officially supported: * All Official Ubuntu variants 12.04 - 18.04 * Debian 6, 7, 8, 9 * Fedora 17 at least * Archlinux * Red Hat * Slackware 14.0 * OpenBSD * NetBSD * FreeBSD 9.2, 10.x, 11.x * openSUSE Tumbleweed (gcc7) * openSUSE Leap 4.2 (gcc4) * SUSE 12 SP3 (gcc4) * Solaris, OpenIndiana 4. Fix. The maintainers of the open source CDE 2.x version have issued the following patches for this vulnerability: https://sourceforge.net/p/cdesktopenv/mailman/message/36900154/ https://sourceforge.net/p/cdesktopenv/code/ci/6b32246d06ab16fd7897dc344db69d0957f3ae08/ Oracle, which maintains a different CDE codebase based on the 1.x train, has assigned the tracking# S1231688 and has released a fix for all affected and supported versions of Solaris in their Critical Patch Update (CPU) of January 2020. As a workaround, it is also possible to remove the setuid bit from the vulnerable executable as follows (note that this might prevent it from working properly): bash-3.2# chmod -s /usr/dt/bin/dtsession Please note that during the audit many other potentially exploitable bugs have surfaced in dtsession and in the Common Desktop Environment in general. Therefore, removing the setuid bit from all CDE binaries is recommended, regardless of patches released by vendors. 5. Proof of Concept. An exploit for Oracle Solaris 10 1/13 (Update 11) Intel has been developed as a proof of concept. It can be downloaded from: https://github.com/0xdea/exploits/blob/master/solaris/raptor_dtsession_ipa.c Copyright (c) 2020 Marco Ivaldi and @Mediaservice.net. All rights reserved.


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