CVE-2025-8818: Linksys RE6250 Firmware RCE Vulnerability

CVE-2025-8818 Overview

CVE-2025-8818 is an operating system (OS) command injection vulnerability affecting multiple Linksys range extenders, including the RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000 product lines through firmware version 20250801. The flaw resides in the setDFSSetting function of the /goform/setLan endpoint. Attackers can manipulate the lanNetmask or lanIp arguments to inject arbitrary operating system commands. The issue is classified under CWE-77 and is exploitable over the network. The vendor was contacted prior to public disclosure but did not respond. A public exploit has been disclosed on GitHub.

Critical Impact
Authenticated attackers can inject arbitrary OS commands into the setLan handler of affected Linksys range extenders, leading to command execution on the embedded device.

Affected Products

Linksys RE6250 firmware 1.0.04.001 and RE6350 firmware 1.0.04.001
Linksys RE6300 firmware 1.2.07.001 and RE6500 firmware 1.0.013.001
Linksys RE7000 firmware 1.1.05.003 and RE9000 firmware 1.0.04.002

Discovery Timeline

2025-08-10 - CVE-2025-8818 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-8818

Vulnerability Analysis

The vulnerability exists in the setDFSSetting function exposed through the /goform/setLan web interface endpoint on affected Linksys range extenders. The handler accepts user-supplied values for lanNetmask and lanIp parameters and passes them to downstream operating system command invocations without proper sanitization or input validation. As a result, an attacker who can reach the device management interface and authenticate with low-privilege credentials can append shell metacharacters to those parameters and have them executed by the underlying operating system shell.

The EPSS score for this issue is approximately 7.66%, placing it in the 93.8th percentile for likelihood of exploitation activity over the next 30 days. A public proof-of-concept is documented in the wudipjq vulnerability repository.

Root Cause

The root cause is improper neutralization of special elements used in an OS command [CWE-77]. The setDFSSetting function concatenates attacker-controlled lanNetmask and lanIp strings into a shell command string that is then handed to a system-level execution primitive. Without input validation, allow-listing, or argument escaping, shell metacharacters such as ;, |, &, and backticks break out of the intended command context.

Attack Vector

The attack is delivered over the network against the web administration interface of the range extender. An attacker submits a crafted HTTP POST request to /goform/setLan with malicious payloads injected into lanNetmask or lanIp. The injected payload executes in the context of the web server process on the embedded device, typically with elevated privileges on consumer-grade firmware. Successful exploitation enables firmware persistence, traffic interception, or pivoting into the local network. See the public PoC for the exact request structure.

Detection Methods for CVE-2025-8818

Indicators of Compromise

HTTP POST requests targeting /goform/setLan containing shell metacharacters (;, |, &, backticks, $()) in the lanNetmask or lanIp parameter values.
Outbound connections originating from a Linksys range extender to unfamiliar IP addresses or download endpoints shortly after configuration changes.
Unexpected processes, cron jobs, or modified startup scripts on the device, observable via syslog forwarded from the extender.

Detection Strategies

Inspect web server access logs on the range extender or upstream proxy for requests to /goform/setLan that contain non-numeric characters in IP or netmask fields.
Deploy network intrusion detection signatures that match shell metacharacters within form-encoded POST bodies destined for Linksys management interfaces.
Correlate administrative HTTP traffic to the extender with subsequent outbound DNS or HTTP requests from that device.

Monitoring Recommendations

Forward syslog from network devices to a centralized log platform and alert on configuration changes to LAN settings.
Baseline expected outbound traffic from infrastructure devices and alert on deviations, especially connections to non-vendor domains.
Monitor for authentication events on the device management interface from unexpected source addresses or at unusual times.

How to Mitigate CVE-2025-8818

Immediate Actions Required

Restrict access to the range extender web management interface to trusted management VLANs or specific administrative hosts only.
Change the default and current administrative credentials on all affected RE-series devices to long, unique passwords.
Disable remote management on the WAN interface if it has been enabled.
Inventory all Linksys RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000 devices and confirm firmware versions against the affected list.

Patch Information

At the time of publication, no vendor patch is referenced in the NVD entry for CVE-2025-8818. The vendor did not respond to the disclosure attempt. Administrators should monitor the Linksys official website for firmware updates addressing the setDFSSetting handler, and consider replacing end-of-life devices that no longer receive security updates.

Workarounds

Place affected range extenders behind a network segment that blocks inbound HTTP/HTTPS connections from untrusted hosts.
Disable any unused management services on the device, including UPnP and remote administration features.
Where business requirements permit, replace affected devices with supported hardware that receives active firmware maintenance.

bash

# Example firewall rule to restrict management access to a single admin host
iptables -A FORWARD -p tcp -d <extender_ip> --dport 80 -s <admin_host_ip> -j ACCEPT
iptables -A FORWARD -p tcp -d <extender_ip> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <extender_ip> --dport 443 -s <admin_host_ip> -j ACCEPT
iptables -A FORWARD -p tcp -d <extender_ip> --dport 443 -j DROP