Post Syndicated from original https://mjg59.dreamwidth.org/56106.html

(Edit: this is CVE-2021-1000002)

Linksys produces a series of wifi mesh routers under the Velop line. These routers use MQTT to send messages to each other for coordination purposes. In the version I tested against, there was zero authentication on this – anyone on the local network is able to connect to the MQTT interface on a router and send commands. As an example:
mosquitto_pub -h 192.168.1.1 -t "network/master/cmd/nodes_temporary_blacklist" -m '{"data": {"client": "f8:16:54:43:e2:0c", "duration": "3600", "action": "start"}}'
will ask the router to block the client with MAC address f8:16:54:43:e2:0c from the network for an hour. Various other MQTT topics pass parameters to shell scripts without quoting them or escaping metacharacters, so more serious outcomes may be possible.

The vendor has released two firmware updates since report – I have not verified whether either fixes this, but the changelog does not indicate any security issues were addressed.

Timeline:

2020-07-30: Submitted through the vendor’s security vulnerability report form, indicating that I plan to disclose in either 90 days or after a fix is released. The form turns out to file a Bugcrowd submission.
2020-07-30: I claim the Bugcrowd submission.
2020-08-19: Vendor acknowledges the issue, is able to reproduce and assigns it a P3 priority.
2020-12-15: I ask if there’s an update.
2021-02-02: I ask if there’s an update.
2021-02-03: Bugcrowd raise a blocker on the issue, asking the vendor to respond.
2021-02-17: I ask for permission to disclose.
2021-03-09: In the absence of any response from the vendor since 2020-08-19, I violate Bugcrowd disclosure policies and unilaterally disclose.

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