CVE-2016-6277

Think of your router like the “front desk” for your internet connection. This bug lets attackers send a specially crafted request to the router’s web-based control area so the router will run commands chosen by the attacker. That can let them take over the router, disrupt internet service, and potentially use your network connection for further attacks.

This matters if your business uses any of the listed NETGEAR router models and they’re running firmware older than the secure versions referenced for CVE-2016-6277. The flaw is reachable over the network from the internet (no login required), because attackers can interact with the router’s exposed configuration web endpoint using a crafted URL. It’s a risk when the router is reachable from the network/internet where the vulnerable web interface can be accessed.

This is RED because confirmed real-world exploitation is reported and it’s listed in CISA’s Known Exploited Vulnerabilities set. Attackers can remotely run arbitrary commands by manipulating the URL path that reaches the router’s cgi-bin/ endpoint, so unpatched routers are actively attractive targets. Treat this as an immediate patching priority.

1. Identify affected hardware: inventory every router in use and match against these NETGEAR models: d6400, d6220, r6250, r6400, r6700, r6900, r7000, r7100lg, r7300dst, r7900.
2. Determine current firmware: for each router, record the exact firmware version currently installed.
3. Check vulnerability status against the vendor’s “before” cutoffs from the CVE description:
   • r6250: before 1.0.4.6.Beta
   • r6400: before 1.0.1.18.Beta
   • r6700: before 1.0.1.14.Beta
   • r6900: (affected; see vendor-secure baseline for your exact branch)
   • r7000: before 1.0.7.6.Beta
   • r7100lg: before 1.0.0.28.Beta
   • r7300dst: before 1.0.0.46.Beta
   • r7900: before 1.0.1.8.Beta
   • d6220, d6400: affected on vulnerable firmware (confirm exact fixed baseline per NETGEAR instructions)
4. Upgrade to the fixed firmware: apply NETGEAR’s remediation steps for CVE-2016-6277 and upgrade to the secure versions indicated in NETGEAR guidance (exact target versions may differ by model/branch).
5. If upgrades are delayed: apply the temporary workaround referenced by NETGEAR for this CVE and reduce exposure as much as possible (e.g., do not expose the router’s management interface to the internet).
6. Post-upgrade verification:
   • Confirm the router comes back cleanly after firmware upgrade.
   • If your router provides logs, check for suspicious requests targeting cgi-bin/ or similar management endpoints.
7. Ongoing monitoring: watch for unexpected reboots, configuration changes, and unusual outbound traffic from the router; these can indicate continuing attacker activity even after partial fixes.

KEV timing note: CISA added this to KEV on 2022-03-07, with a remediation due date of 2022-09-07.

CVE-2016-6277 is a high-severity (CVSS 8.8) unauthenticated remote command execution vulnerability mapped to CWE-352 (command injection). The mechanism is triggered by sending a crafted request to the router’s web configuration cgi-bin/ endpoint with special characters in the URL path, enabling the attacker to run arbitrary commands on the device. Findings indicate reachable-by-default in the affected routers, with no authentication required. Real-world exploitation is confirmed via KEV listing (CISA) and reports of active incidents; an in-the-wild botnet context is also noted. Public exploits exist, which lowers the attacker effort. The traffic-light verdict is RED due to confirmed exploitation in the wild (KEV/news), not just predicted risk.