CVE-2025-5440 Overview
CVE-2025-5440 is an operating system command injection vulnerability affecting multiple Linksys range extender models, including the RE6500, RE6250, RE6300, RE6350, RE7000, and RE9000. The flaw resides in the NTP function exposed through the /goform/NTP endpoint. Attackers can manipulate the manual_year_select, manual_month_select, manual_day_select, manual_hour_select, manual_min_select, and manual_sec_select arguments to inject arbitrary operating system commands. The vulnerability is exploitable over the network and the exploit details have been publicly disclosed. According to the CVE record, the vendor was contacted before disclosure but did not respond.
Critical Impact
Authenticated attackers can inject arbitrary operating system commands through the NTP configuration endpoint, leading to remote code execution on affected Linksys range extenders.
Affected Products
- Linksys RE6500 firmware 1.0.013.001
- Linksys RE6250 / RE6350 firmware 1.0.04.001 and RE9000 firmware 1.0.04.002
- Linksys RE7000 firmware 1.1.05.003 and RE6300 firmware 1.2.07.001
Discovery Timeline
- 2025-06-02 - CVE-2025-5440 published to NVD
- 2025-07-02 - Last updated in NVD database
Technical Details for CVE-2025-5440
Vulnerability Analysis
The vulnerability is classified under [CWE-77] Improper Neutralization of Special Elements used in a Command. The affected Linksys range extenders expose a web management interface that handles Network Time Protocol (NTP) configuration through the /goform/NTP endpoint. The NTP handler accepts user-supplied date and time parameters but fails to sanitize the input before passing values to an underlying shell command. Attackers can therefore embed shell metacharacters within the manual time fields to break out of the intended command context. The EPSS score is 5.393% with a 90.269 percentile, indicating elevated probability of exploitation compared to most published CVEs.
Root Cause
The root cause is missing input neutralization in the NTP handler of /goform/NTP. User-controlled fields including manual_year_select, manual_month_select, manual_day_select, manual_hour_select, manual_min_select, and manual_sec_select are concatenated into a shell command without escaping or argument validation. Any shell metacharacter supplied in these fields is interpreted by the underlying operating system.
Attack Vector
The attack vector is network-based and requires low privileges. An attacker who can reach the device web interface, typically over the local area network or via an exposed management portal, submits a crafted POST request to /goform/NTP. Injected commands execute with the privileges of the web server process, which on consumer-grade Linksys range extenders generally runs as root. A complete technical write-up is available in the GitHub Vulnerability Description and the VulDB entry #310779.
No verified exploit code is reproduced here. The referenced advisory describes how shell metacharacters appended to the manual time selection arguments cause the device to execute attacker-supplied commands during NTP configuration.
Detection Methods for CVE-2025-5440
Indicators of Compromise
- HTTP POST requests to /goform/NTP containing shell metacharacters such as ;, |, &&, or backticks in the manual_*_select parameters.
- Unexpected outbound connections from range extender management IP addresses to unknown hosts following NTP configuration changes.
- Modifications to device configuration, firmware, or persistent storage that do not correlate with administrator activity.
Detection Strategies
- Inspect web server and reverse proxy logs for requests targeting /goform/NTP with non-numeric values in the manual date and time fields.
- Deploy network intrusion detection signatures that flag command injection patterns in HTTP POST bodies destined for Linksys management interfaces.
- Correlate authentication events on the range extender with subsequent NTP configuration changes to identify unauthorized access.
Monitoring Recommendations
- Forward range extender syslog output to a centralized logging platform and alert on configuration changes outside maintenance windows.
- Monitor DNS and egress traffic from network appliances for indicators of reverse shells, cryptominers, or botnet activity.
- Track firmware versions across the fleet to identify devices still running vulnerable builds such as 1.0.013.001, 1.0.04.001, 1.0.04.002, 1.1.05.003, and 1.2.07.001.
How to Mitigate CVE-2025-5440
Immediate Actions Required
- Restrict access to the range extender web management interface to trusted management VLANs and block exposure to the internet.
- Change default and weak administrative credentials, since exploitation requires low-privilege authenticated access.
- Audit recent activity on affected devices for signs of unauthorized configuration changes or persistence.
Patch Information
No vendor patch or security advisory has been published at the time of this writing. The CVE record states that Linksys did not respond to the disclosure. Organizations should consult the Linksys Official Website for any future firmware updates and replace end-of-life models that no longer receive security maintenance.
Workarounds
- Place affected Linksys range extenders behind a firewall that blocks inbound access to /goform/NTP from untrusted networks.
- Disable remote administration features and require VPN access for management traffic.
- Replace vulnerable RE6500, RE6250, RE6300, RE6350, RE7000, and RE9000 units with currently supported hardware where feasible.
# Example firewall rule to restrict management access to the range extender
iptables -A FORWARD -p tcp -d <range_extender_ip> --dport 80 -s <mgmt_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <range_extender_ip> --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
