CVE-2021-40847: NETGEAR r6400v2 Firmware

High severity, CVSS 8.1. EPSS: 10% chance of exploitation in the next 30 days.

The update process of the Circle Parental Control Service on various NETGEAR routers allows remote attackers to achieve remote code execution as root via a MitM attack. While the parental controls themselves are not enabled by default on the routers, the Circle update daemon, circled, is enabled by default. This daemon connects to Circle and NETGEAR to obtain version information and updates to the circled daemon and its filtering database. However, database updates from NETGEAR are unsigned and downloaded via cleartext HTTP. As such, an attacker with the ability to perform a MitM attack on the device can respond to circled update requests with a crafted, compressed database file, the extraction of which gives the attacker the ability to overwrite executable files with attacker-controlled code. This affects R6400v2 1.0.4.106, R6700 1.0.2.16, R6700v3 1.0.4.106, R6900 1.0.2.16, R6900P 1.3.2.134, R7000 1.0.11.123, R7000P 1.3.2.134, R7850 1.0.5.68, R7900 1.0.4.38, R8000 1.0.4.68, and RS400 1.5.0.68.

Affected products

NETGEAR r6400v2 Firmware: version 1.0.4.106 only
NETGEAR r6700 Firmware: version 1.0.2.16 only
NETGEAR r6700v3 Firmware: version 1.0.4.106 only
NETGEAR r6900 Firmware: version 1.0.2.16 only
NETGEAR r6900p Firmware: version 1.3.2.134 only
NETGEAR r7000 Firmware: version 1.0.11.123 only
NETGEAR r7000p Firmware: version 1.3.2.134 only
NETGEAR r7850 Firmware: version 1.0.5.68 only
NETGEAR r7900 Firmware: version 1.0.4.38 only
NETGEAR r8000 Firmware: version 1.0.4.68 only
NETGEAR RS400 Firmware: version 1.5.0.68 only

Published 2021-09-21. Last modified 2026-06-17.