CVE-2018-25396 Overview
CVE-2018-25396 is a credential disclosure vulnerability in Heatmiser Wifi Thermostat version 1.7. The device exposes administrative credentials through the networkSetup.htm page without requiring authentication. Unauthenticated attackers on the network can request this endpoint and extract plaintext username and password values from HTML form fields. Successful exploitation grants full administrative access to the thermostat. The flaw is categorized under [CWE-256] (Plaintext Storage of a Password) and affects the device's web management interface.
Critical Impact
Unauthenticated network attackers can retrieve administrative credentials in plaintext from the networkSetup.htm page, enabling full takeover of the affected Heatmiser Wifi Thermostat.
Affected Products
- Heatmiser Wifi Thermostat version 1.7
- Web management interface exposing networkSetup.htm
- Deployments where the thermostat is reachable over LAN or the internet
Discovery Timeline
- 2026-05-29 - CVE-2018-25396 published to NVD
- 2026-06-01 - Last updated in NVD database
Technical Details for CVE-2018-25396
Vulnerability Analysis
The Heatmiser Wifi Thermostat 1.7 serves a network configuration page at networkSetup.htm through its embedded web server. The page is intended for administrative use but lacks any authentication enforcement. When an HTTP client requests the URL, the device returns the full HTML page including pre-populated form fields. These fields contain the current administrative username and password in cleartext within value attributes. An attacker who can reach the device on the network can issue a single HTTP GET request and parse the response to recover the credentials. The credentials then permit login to the administrative interface, enabling configuration changes, heating schedule manipulation, and pivoting on the local network.
Root Cause
The root cause is plaintext storage and disclosure of credentials in the web interface, mapped to [CWE-256]. The configuration page renders stored credential values directly into the HTML response without masking, redaction, or access control. Combined with the absence of an authentication check on the endpoint, any network-adjacent actor can read the values.
Attack Vector
The attack vector is network-based and requires no privileges or user interaction. An attacker sends an HTTP GET request to http://<thermostat-ip>/networkSetup.htm and inspects the returned HTML. Credential values appear inside <input> element value attributes and can be extracted with simple string parsing or a regular expression. No exploit code is required beyond a standard HTTP client such as curl or a browser. A public advisory is documented in Exploit-DB #45623 and the VulnCheck Advisory.
Detection Methods for CVE-2018-25396
Indicators of Compromise
- HTTP GET requests to /networkSetup.htm from unexpected source addresses in thermostat or upstream router logs.
- Administrative logins to the thermostat from IP addresses outside the normal management range.
- Unexplained configuration changes to network or heating settings on the device.
Detection Strategies
- Inspect HTTP traffic to Heatmiser thermostats for requests to networkSetup.htm and flag any without a prior authenticated session.
- Deploy network sensors that decode HTTP responses and alert when responses contain credential-shaped form fields from IoT endpoints.
- Correlate device administrative actions with the source IP of preceding networkSetup.htm requests.
Monitoring Recommendations
- Enable verbose logging on the network segment hosting building automation devices and forward logs to a central SIEM.
- Continuously scan internal ranges for Heatmiser web interfaces exposed beyond their intended management VLAN.
- Alert on any external internet-sourced connection attempts to the thermostat's HTTP port.
How to Mitigate CVE-2018-25396
Immediate Actions Required
- Remove the thermostat from any internet-exposed interface and place it behind a firewall restricted to authorized management hosts.
- Rotate any credentials previously stored on the device, including any reused passwords on related systems.
- Audit access logs for prior requests to networkSetup.htm from unexpected sources.
Patch Information
No vendor patch is referenced in the available advisory data. Operators should consult Heatmiser support for current firmware status and apply any updated firmware that removes credential exposure from networkSetup.htm. Until a fix is confirmed, treat the device as a compromised-by-design endpoint and apply network-layer controls.
Workarounds
- Segment Heatmiser thermostats onto an isolated VLAN with strict ACLs that permit only authorized management workstations.
- Block inbound access to the device's HTTP port at the perimeter firewall to prevent internet-based exploitation.
- Place the device behind a reverse proxy that enforces authentication before forwarding requests to networkSetup.htm.
- Disable remote management features if they are not required for operational use.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
