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CableTap/doc/advisories/bastille-22.syseventd.txt
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| Bastille Tracking Number 22 | |
| CVE-2017-9479 | |
| Overview | |
| A vulnerability has been discovered that enables an attacker to launch applications on a gateway as a root user. This vulnerability can be exploited by an attacker connected to the LAN, private Wi-Fi AP, or Xfinity Home Security AP. | |
| Affected Platforms | |
| Cisco DPC3939, firmware version dpc3939-P20-18-v303r20421746-170221a-CMCST | |
| Proof-of-Concept | |
| The syseventd service provides a mechanism to launch applications on the gateway in response to certain events, such as the one-minute cron job firing. The sysevent command line application is used to communicate with the syseventd server, which is open on port 52378 to the LAN, private Wi-Fi AP, and Xfinity Home Security Wi-Fi AP. | |
| An attacker on one of the above networks can take advantage of this, using the sysevent command line application to launch applications on the gateway. | |
| The following two commands, when executed from a computer connected to an Xfinity Home Security Wi-Fi AP, will cause the persistent storage configuration data to be copied to /var/IGD/. This can then be retrieved by the attacker. | |
| ./sysevent --port 52367 --ip 172.16.12.1 async </path/to/file> /bin/cp | |
| ./sysevent --port 52367 --ip 172.16.12.1 set </path/to/file> /var/IGD/<file> | |
| Test Environment | |
| Cisco DPC3939, firmware version dpc3939-P20-18-v303r20421746-170221a-CMCST | |
| Mitigation | |
| There is no apparent mechanism to allow Comcast customers to disable syseventd access. | |
| Recommended Remediation | |
| Update the firewall rules to disable access to syseventd from the LAN, private Wi-Fi AP, and Xfinity Home Security Wi-Fi AP. | |
| Credits | |
| Marc Newlin and Logan Lamb, Bastille | |
| Chris Grayson, Web Sight.IO |