CVE-2025-1204: Firmware Authentication Bypass Vulnerability

CVE-2025-1204 Overview

CVE-2025-1204 affects the update binary in firmware shipped with the Contec CMS8000 patient monitor family. The binary attempts to mount a remote share at a hard-coded, routable IP address, ignoring the device's configured network settings. The mount routine triggers when the C button is pressed at a specific moment during the boot sequence. An attacker who controls or impersonates the hard-coded IP address can upload and overwrite files on the device, including executable content used by the firmware.

The weakness is tracked as CWE-912: Hidden Functionality and was documented in CISA Medical Advisory ICSMA-25-030-01 and Claroty Team82 research.

Critical Impact

An attacker who controls the hard-coded IP address can overwrite firmware files on affected patient monitors, leading to integrity loss and potential code execution on medical devices.

Affected Products

• Contec CMS8000 patient monitors (firmware containing the update binary)
• Rebranded variants of the same firmware platform identified by Claroty Team82
• Devices reachable on networks where the hard-coded routable IP can be impersonated

Discovery Timeline

• 2025-02-25 - CVE-2025-1204 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-1204

Vulnerability Analysis

The update binary contains a hidden routine activated by holding the C button at a specific point in the boot process. When triggered, the binary issues a mount request to a hard-coded, routable IP address rather than any address derived from the device's runtime network configuration. The mounted remote filesystem is then used as a source for files that can replace content on the local device.

Because the destination IP is hard-coded and routable on the public internet, any party that controls that address — through routing manipulation, BGP hijacking, DNS-independent IP impersonation, or simply by registering services on that address — becomes a trusted source of firmware-level files. The device performs no cryptographic verification of the mounted content described in the advisory, so overwritten files execute with the privileges of the update process.

Root Cause

The root cause is hidden functionality embedded in the firmware [CWE-912]. The developer included an undocumented mount-and-update path bound to a static IP literal, bypassing the device's own network and security configuration. Trust is placed in the network endpoint rather than in signed update packages.

Attack Vector

Exploitation requires the boot-time button press, which limits remote, fully unauthenticated mass exploitation. However, an attacker with brief physical access, or an insider in a clinical environment, can trigger the routine. Once triggered, the device pulls files from whatever host answers at the hard-coded IP. An attacker controlling that IP can deliver arbitrary replacement files to the monitor, affecting confidentiality, integrity, and availability of the medical device.

No verified public proof-of-concept code is associated with this CVE. Technical details are described in the Claroty Team82 research linked above.

Detection Methods for CVE-2025-1204

Indicators of Compromise

• Outbound connection attempts from patient monitors to the hard-coded routable IP address identified in the Claroty research and CISA ICSMA-25-030-01 advisory
• NFS or SMB mount traffic originating from medical device VLANs to external destinations
• Unexpected modification timestamps on firmware files following a device reboot or maintenance event

Detection Strategies

• Inspect network flow data and firewall logs for traffic from biomedical device subnets to the hard-coded IP documented in vendor and CISA advisories
• Apply deep packet inspection to detect mount protocol traffic (NFS/CIFS) leaving clinical network segments
• Compare firmware file hashes against a known-good baseline after any boot event involving the C button

Monitoring Recommendations

• Place CMS8000 devices on isolated VLANs with egress filtering that blocks all traffic except to approved clinical systems
• Forward firewall and netflow telemetry from medical device segments to a central analytics platform to correlate anomalous outbound destinations
• Alert on any boot-time button sequences logged by physical access monitoring where available

How to Mitigate CVE-2025-1204

Immediate Actions Required

• Block outbound traffic from CMS8000 devices to the hard-coded IP address identified in CISA ICSMA-25-030-01 at the perimeter and internal firewalls
• Restrict physical access to the front panel of affected monitors to authorized clinical staff only
• Inventory all CMS8000 and rebranded units to determine firmware versions in use

Patch Information

At the time of NVD publication, no vendor firmware patch is referenced in the advisory data. CISA recommends network-level mitigations and following guidance in ICSMA-25-030-01 until a corrected firmware is released. Consult Contec or the device reseller for firmware status before deploying any update.

Workarounds

• Segment patient monitors onto a dedicated VLAN with no route to the public internet
• Configure egress access control lists to deny traffic to the hard-coded IP and to all non-clinical destinations
• Disable or physically cover the C button on devices that do not require it for clinical workflows, where vendor guidance permits
• Treat any device that has been booted with the C button held as potentially compromised and reimage from known-good media