Unsigned firmware loading and hard-coded network beacon

1. Summary

The Contec CMS8000 patient monitor (also sold as the Epsimed MN-120) runs a monolithic ARM firmware application whose “monitor”/“update” logic mounts an NFS share from a hard-coded, routable public IP address and copies the fetched files into its own executable directory with no cryptographic signature verification. Any host able to answer at that hard-coded address can therefore supply the code the device executes as root. The same firmware, by default, transmits patient health information (PHI) in plaintext to that same hard-coded external host whenever a patient is connected. A separate out-of-bounds write in the device’s UDP-facing code additionally permits unauthenticated remote code execution. An attacker who can reach or impersonate the hard-coded host gains the ability to overwrite trusted monitor code, and a network-adjacent observer can read unencrypted PHI.

2. Affected products & versions

3. The vulnerability in detail

Where the flaw lives. The defect sits inside the monolithic ARM firmware application that runs the monitor. Specifically, the “monitor” binary embeds firmware-upgrade logic, and an “update” binary performs a network mount [4][6]. This is not a discrete, network-listening update service in the conventional sense; the update behavior is woven into the main application that also drives what appears on the screen. Two additional, independent defects live in adjacent parts of the same firmware: a default PHI-transmission behavior, and an out-of-bounds write in the network-facing UDP handling code [5][8].

Root cause — a missing firmware/update trust root. The core defect is that the device has no trust anchor for the code it runs. During its update path the binary issues, in effect, mount -o nolock -t nfs 202.114.4.119:/pm /mnt, checks for the existence of /mnt/monitor, and then runs cp -rf /mnt/* /opt/bin, copying the downloaded files straight into its executable directory with no cryptographic signature verification of what it just fetched [6]. Two properties make this dangerous. First, the destination IP 202.114.4.119 is hard-coded and routable on the public internet, and the update function bypasses the device’s own network configuration — re-enabling the network interface if an operator had disabled it [4][6]. Second, because there is no signature check, any host that can answer at that address is implicitly trusted to supply root-executed code. That is a firmware/update trust-root failure. CISA and NVD frame this as CWE-912 (Hidden Functionality) for CVE-2025-0626 — the idea being that the device contains behavior, undocumented to operators, that reaches out to an external address and can pull in and run new code [4]. The monitor will run whatever binary a party at a fixed external IP hands it, and it does so without ever asking “is this code from someone I trust?”

A second, independent root cause is a design default that leaks PHI. In its default state, when a patient is connected, the device transmits plaintext patient data to a hard-coded public IP (CWE-359, Exposure of Private Personal Information to an Unauthorized Actor) [5]. The reported fields include doctor name, patient ID, patient name, patient date of birth, and other monitoring information, reportedly over port 515 (LPD) [7] — though the port attribution is press-sourced and not specified in the NVD record [5].

A third, independent root cause is an out-of-bounds write (CWE-787) reachable via specially formatted UDP requests, allowing an attacker to write arbitrary data and achieve remote code execution with no authentication and no user interaction (CVE-2024-12248) [8].

Mechanism and how it is triggered. Three distinct mechanisms share the theme of trusting an untrusted remote host:

1. Insecure update / hard-coded mount (CVE-2025-0626, CVE-2025-1204). The binary performs the NFS mount to 202.114.4.119:/pm, verifies /mnt/monitor exists, then copies everything into /opt/bin, overwriting the device’s own executables with no signature check [6]. The function re-enables the network interface if it was disabled [4]. As to what triggers it, the two sources diverge on the precondition. CISA/NVD framing describes the behavior activating during device update attempts [4]. Claroty Team82, reverse-engineering the same firmware, could only trigger the update logic by booting the device and pressing the physical ‘C’ (main) button at a specific point during boot [6]. NVD’s record for CVE-2025-1204 aligns with Team82: the “update” binary mounts to the hard-coded routable IP, bypassing device network settings, triggered if ‘C’ is pressed at a specific time during boot [6]. Either way, the attacker precondition is the same — the ability to answer at, or impersonate, the hard-coded host — and the device requires no authentication of that host.

2. Plaintext PHI egress (CVE-2025-0683). No attacker action is needed. In the default configuration, connecting a patient causes the device to emit plaintext PHI to the hard-coded public IP, exposing it to any host at that address or to an adversary-in-the-middle on the path [5][7].

3. OOB-write RCE (CVE-2024-12248). An attacker with network reachability sends specially formatted UDP requests; the malformed input drives an out-of-bounds write of arbitrary data, which is leveraged into remote code execution. It is network-accessible with no authentication and no user interaction (CVSS v4 AV:N/AC:L/AT:N/PR:N/UI:N) [8].

Step-by-step exploitation chain.

Path A — insecure update / RCE via the hard-coded host (CVE-2025-0626 / CVE-2025-1204):

1. Attacker gains a position to answer at, or impersonate, the hard-coded IP 202.114.4.119 — on-path/adjacent network, BGP/DNS/route manipulation, or by controlling that address [6][7].
2. The device’s monitor/update binary — at boot with the ‘C’ button pressed (per Team82), or during an update attempt (per CISA/NVD) — issues the NFS mount of 202.114.4.119:/pm to /mnt, ignoring local network configuration and re-enabling the interface if disabled [6][4].
3. The binary copies attacker-supplied files (cp -rf /mnt/* /opt/bin) into its executable directory with no signature verification, overwriting trusted monitor code [6].
4. The device executes the attacker’s binaries as root on the next run, yielding remote code execution and full control over what the monitor displays and does; because the original files are overwritten, the hospital loses awareness of what software is actually running [6][7].

Path B — unauthenticated OOB-write RCE (CVE-2024-12248):

1. Attacker with network reachability sends specially formatted UDP requests to the device [8].
2. The malformed UDP input triggers an out-of-bounds write of arbitrary data [8].
3. The write is leveraged into remote code execution with no authentication or user interaction [8].

Path C — PHI disclosure (CVE-2025-0683):

1. A patient is connected to the monitor in its default configuration [5].
2. The device transmits plaintext PHI (doctor name, patient ID, name, DOB, monitoring info) to the hard-coded public IP [5][7].
3. Any host at that address, or an adversary-in-the-middle, reads the unencrypted PHI [5].

Proof-of-concept status. A working RCE proof-of-concept exists: Claroty Team82 demonstrated RCE by impersonating the hard-coded IP and delivering a malicious binary that ran a reverse shell / arbitrary commands as root; this insecure-update mechanism is tracked as CVE-2025-1204 [6].

The underlying weaknesses (CWE-912, CWE-359, CWE-787). CWE-912 (Hidden Functionality) captures the update/trust-root defect: the firmware contains behavior — reaching out to a fixed external address and pulling down executable code — that is not exposed to or controllable by the operator through the device’s own configuration, and which bypasses that configuration. CWE-359 (Exposure of Private Personal Information to an Unauthorized Actor) captures the PHI leak: sensitive personal data is sent, unencrypted and by default, to a party who has no authorization to receive it. CWE-787 (Out-of-bounds Write) captures the memory-corruption RCE: attacker-controlled input causes a write past the bounds of an intended buffer, corrupting memory in a way that an attacker steers toward arbitrary code execution.

4. Discovery & timeline

An external/anonymous security researcher disclosed the vulnerabilities to CISA, which then reverse-engineered three firmware package versions [7]. Independently, Claroty Team82 reverse-engineered the firmware, published a reframing analysis, and built the RCE PoC that became CVE-2025-1204 [6]. Team82 notes the underlying RCE was first demonstrated at their 2022 Nexus Conference [6].

• 2025-01-30 — CISA published its fact sheet and alert, with the ICS-Medical advisory ICSMA-25-030-01 (Update A) following; it was publicly reported the same day [3][7][8].
• ~2025-01-31 — public reporting [8].
• ~2025-02-04 — Claroty Team82 published its contrarian analysis [7] (approximate; exact publication date not confirmed in the available sources).

FDA issued a coordinated safety communication [7][8]. Exact vendor-notification / pre-disclosure coordination dates are not detailed in the available sources.

5. Technical reference

What the key metrics mean here. For CVE-2025-0626, the v4 vector shows a network attack vector (AV:N) but AT:P (a present attack requirement) and UI:P (passive user interaction) — consistent with the real-world precondition that an attacker must be positioned at the hard-coded host and, per Team82, the physical ‘C’-button boot condition must be met; the high VC/VI/VA reflects full confidentiality, integrity, and availability impact once trusted code is overwritten. For CVE-2025-0683, UI:N and high VC with no integrity/availability impact match a passive, no-interaction confidentiality leak; note the v3.1 vector carries AC:H, which is why the v3.1 base score (5.9) sits below the v4 score (8.2) — the older metric penalizes the on-path positioning as high attack complexity [5]. For CVE-2024-12248, the near-maximal 9.3/9.8 reflects the absence of any attack requirement, privilege, or user interaction — pure unauthenticated network RCE.

Code/commit refs: No source-repository commits (this is closed firmware). The concrete code artifacts identified by researchers are the monitor/update binaries, the NFS mount 202.114.4.119:/pm → /mnt, and the copy cp -rf /mnt/* /opt/bin into /opt/bin [6].

6. Consequence & CFSE path analysis

Real-world consequence. In a hospital deployment, three concrete harms can occur. (a) An attacker positioned at the hard-coded external host can replace the monitor’s software with their own, running as root, while the device hides that fact from staff because the original files are overwritten. (b) That attacker-controlled or corrupted monitor can then display false vital signs or suppress alarms — a wrong-care safety pathway. (c) Even absent any attacker, the device leaks identifiable patient data in plaintext to an external address by default. All three stem from one shared root cause: a monitor that trusts an unauthenticated, hard-coded external host and has no signed-update recovery path.

Why the CFSE Path Score diverges from CVSS. The published CVSS baselines (7.7 for the hidden-functionality/trust-root flaw, 8.2 for the PHI egress; 9.3/9.8 for the separate OOB-write RCE) score each CVE as an isolated defect. The CFSE analysis instead recognizes that a single trust-root failure forks into three simultaneous terminal harms, and scores each terminal path in its own harm family rather than collapsing them into one baseline number. The CVSS view understates the aggregate because it does not represent the chain (one root cause → three co-dominant harms), the narrative-invariance concern, or the absence of any recovery path.

Carried CFSE bands / verdict from seed:

Verdict: CRITICAL. The existing analysis scores three co-dominant terminal paths, all in the CRITICAL band, stemming from one shared root cause: the CMS8000 mounts NFS from a hard-coded routable IP and copies binaries into its executable directory with no signature check (forcing the network interface up), and by default beacons plaintext patient health information (PHI) to that same hard-coded address.

• Path 1 — firmware-trust-root (authority family): treats unsigned binaries run as trusted monitor code as a firmware trust-root failure.
• Path 2 — device-control-safety (safety family): covers malicious code falsifying displayed vitals or suppressing alarms, a serious wrong-care safety pathway asserted without claiming observed field injury.
• Path 3 — data-privacy (privacy family): covers the default plaintext PHI egress to the hard-coded external host.

The record notes the published 7.7/8.2 CVSS baseline collapses what is really one trust-root failure forking into three simultaneous terminal harms, and flags no signed-update recovery path plus a narrative divergence (CISA’s “backdoor”/CWE-912 framing versus Claroty Team82’s “insecure design, documented default” read). Consequence drivers cited are requirement #2 (chain/multi-path), #7 (narrative-invariance), and #8 (recoverability).

The safety path (Path 2) is asserted as a plausible terminal harm — an attacker with root code execution on a monitor can manipulate what clinicians see — not as an observed field injury; FDA reported no known incidents [8]. The recoverability driver (#8) is grounded: because there is no signed-update mechanism, there is no in-band trusted way to deliver a fix, which is why CISA’s guidance is network isolation and disconnection rather than “patch” [7][8].

7. Remediation & mitigations

No vendor patch or signed-firmware update is documented in the available sources; there is no signed-update mechanism to deliver a trusted fix, which is why remediation is network-level and physical rather than a firmware upgrade [7][8]. Specific, grounded measures:

• Remove/disconnect affected monitors from any network where clinically feasible [7][8].
• Block outbound traffic to the hard-coded destination. CISA guidance quoted as blocking all access to subnet 202.114.4.0/24 from the internal network and blocking outbound traffic to 202.114.4.120 [8]; block the hard-coded CMS IP 202.114.4.119 at the firewall [7]. (Note the IP discrepancy between 202.114.4.119 and 202.114.4.120 across sources; blocking the full /24 covers both.)
• Because the update path bypasses local network config and re-enables the interface, host-side disabling of networking on the device is not reliable as a mitigation — the firmware can force the interface back up [4]. Network-boundary blocking is the load-bearing control.
• FDA issued a coordinated safety communication as part of the response [7][8].

8. Sources

[1] Contec Health CMS8000 Patient Monitor (Update A) — ICSMA-25-030-01 — CISA (ICS-Medical Advisory) — https://www.cisa.gov/news-events/ics-medical-advisories/icsma-25-030-01 — Authoritative advisory enumerating all three CVEs, affected products, CVSS scores/vectors, technical description, and mitigations; the primary evidence anchor. Credibility: primary-advisory.

[2] Contec CMS8000 Contains a Backdoor — CISA Fact Sheet (TLP:CLEAR PDF) — CISA — https://www.cisa.gov/sites/default/files/2025-01/fact-sheet-contec-cms8000-contains-a-backdoor-508c.pdf — CISA’s reverse-engineering fact sheet establishing the “backdoor”/hidden-functionality framing, malicious IP indicators, and remove-from-networks guidance; drives the narrative-divergence point. Credibility: primary-advisory.

[3] CISA Releases Fact Sheet Detailing Embedded Backdoor Function of Contec CMS8000 Firmware — CISA — https://www.cisa.gov/news-events/alerts/2025/01/30/cisa-releases-fact-sheet-detailing-embedded-backdoor-function-contec-cms8000-firmware — Dated alert page (2025-01-30) anchoring the official timeline and government framing. Credibility: primary-advisory.

[4] NVD — CVE-2025-0626 — NVD (NIST) — https://nvd.nist.gov/vuln/detail/CVE-2025-0626 — Canonical record for the hidden-functionality/hard-coded-IP flaw; CWE-912, CVSS v4.0 7.7 and v3.1 7.5, and the hard-coded-IP/interface/overwrite description. Credibility: primary-advisory.

[5] NVD — CVE-2025-0683 — NVD (NIST) — https://nvd.nist.gov/vuln/detail/CVE-2025-0683 — Canonical record for the PHI-exposure CVE (CWE-359); documents default plaintext PHI transmission to a hard-coded public IP and the 8.2 headline score (v3.1 5.9, vector AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N); no port specified. Credibility: primary-advisory.

[6] Do the CONTEC CMS8000 Patient Monitors Contain a Chinese Backdoor? The Reality is More Complicated… — Claroty Team82 — https://claroty.com/team82/research/are-contec-cms8000-patient-monitors-infected-with-a-chinese-backdoor-the-reality-is-more-complicated — Independent reverse-engineering reframing the flaw as insecure design (IP documented in the operator manual as the CMS address; update needs a physical button press) and reporting a working RCE PoC (CVE-2025-1204); source for the exact mount/copy commands and the narrative-invariance argument. Credibility: researcher-primary.

[7] Backdoor found in two healthcare patient monitors, linked to IP in China — BleepingComputer — https://www.bleepingcomputer.com/news/security/backdoor-found-in-two-healthcare-patient-monitors-linked-to-ip-in-china/ — Reputable press confirming both affected devices, the CISA/FDA coordinated response, the PHI fields and reported port 515/LPD, and hard-coded IP indicators. Credibility: reputable-press.

[8] CISA and FDA Warn of Critical Backdoor in Contec CMS8000 Patient Monitors — The Hacker News — https://thehackernews.com/2025/01/cisa-and-fda-warn-of-critical-backdoor.html — Press summary spanning all three CVEs including CVE-2024-12248 (OOB write, 9.3/9.8, unauthenticated UDP RCE), FDA safety communication, affected firmware versions, and the 202.114.4.0/24 block guidance. Credibility: reputable-press.