CVE-2025-59668 NULL Pointer DoS in CNS-6201 Central Monitor

The newly disclosed vulnerability in NIHON KOHDEN’s Central Monitor CNS-6201 (CVE-2025-59668) is a straightforward but dangerous example of how a simple memory-handling bug in an end‑of‑life medical device can translate into an operational safety problem for hospitals and clinical networks. A remotely delivered, specially crafted UDP packet can trigger a NULL pointer dereference that causes the monitoring process to terminate and the device to enter a denial‑of‑service (DoS) state; the flaw affects multiple CNS‑6201 firmware revisions and requires no authentication to exploit. Public records and vendor notices list an overall severity in the high range (CVSS v3.1 ≈ 7.5; CVSS v4 ≈ 8.7), and the maintainers and national coordinators recommend discontinuing use of the affected versions and applying strict network compensations where replacement is not yet possible.

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Background / Overview​

The CNS‑6201 is a central nursing/central monitoring station used to aggregate bedside vital signs and alarms from multiple patient monitors. These central stations are often deployed in critical care units, step‑down wards, and other multi‑patient monitoring environments where availability is essential to patient safety. NIHON KOHDEN’s product documentation confirms the CNS‑6201 as a core central station product in their portfolio.
On September 30, 2025 the issue was publicly recorded as CVE‑2025‑59668 by vulnerability coordinators and tracked by national and international repositories. The vulnerability is described as a NULL pointer dereference (CWE‑476) that is triggered when the device’s UDP service processes a specially crafted packet. Multiple independent trackers and vulnerability databases (including JVN and NVD summaries) list the same affected version set and scoring. JVN’s advisory explicitly lists the affected CNS‑6201 firmware versions and states the product versions referenced are no longer supported; NVD reproduces the CVE metadata and confirms the NULL pointer dereference classification.
Why this matters: central stations like the CNS‑6201 are not peripheral telemetry devices; they are the clinical view of multiple patients. A crash or process termination that disables alarm aggregation, alarm escalation, or visibility of bedside alarms can—and in worst cases will—delay clinical response or require manual workaround procedures that increase cognitive load on staff and risk for patients.

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Technical summary: what the bug is and how it behaves​

• Vulnerability class: NULL pointer dereference (CWE‑476).
• Trigger: A specially crafted UDP packet sent to the device’s network service.
• Authentication: None required — the attacker needs only network reachability.
• Primary impact: Availability — process termination/DoS, not data disclosure or code execution (as published).
• Affected versions: CNS‑6201 versions 01‑03, 01‑04, 01‑05, 01‑06, 02‑10, 02‑11, 02‑40 (per vendor/JVN listings).
• Scoring: CVSS v3.1 base ≈ 7.5; CVSS v4 base ≈ 8.7 (availability‑focused).

A NULL pointer dereference occurs when software dereferences a pointer that contains a NULL (zero/invalid) value. In embedded and real‑time systems this commonly causes the receiving process or task to crash or enter a fatal error state. In network‑connected medical devices the receiving packet handler is often exposed to maintenance and integration networks; if the UDP service is reachable from a broader network zone, an unauthenticated remote actor can trigger the condition with crafted datagrams. The result is a reproducible crash (or abnormal process termination) that disrupts monitoring. For broader technical context on this class of failures in OT/medical devices and why they translate into operational‑level outages, see established CISA/industry advisories describing NULL pointer dereference DoS patterns and recommended compensating controls.

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What is confirmed and what remains uncertain​

Confirmed by multiple authoritative sources:

• The bug is a NULL pointer dereference triggered by malformed UDP input.
• Affected CNS‑6201 firmware versions include the lists published by JVN and vendor advisories.
• Exploitation does not require authentication and is reproducible when the UDP service is reachable.

Unverified / not claimed:

• There is no publicly available evidence of active exploitation in the wild at the time of public disclosure; EPSS/telemetry scores and vulnerability trackers indicate low-to-negligible exploit telemetry or proof‑of‑concept release. Treat the “no known exploitation” status as time‑sensitive—weaponization risk increases once code or test vectors appear.
• There is no vendor firmware patch publicly distributed for those specific EOL version numbers at the time of initial reporting; the vendor and national coordinators recommend discontinuation of affected versions and migration to supported successors where available. Verify vendor‑side advisories for updates.

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Risk evaluation: clinical and operational impact​

The practical risk model for this vulnerability centers on availability and safety:

• Availability risk to clinicians: a central station process crash can remove consolidated alarms and visual cues that staff depend on, forcing manual checks or local bedside monitoring workarounds. In busy units this materially increases the chance that critical alarms are delayed or missed.
• Operational continuity: repeated or targeted DoS events could create intermittent visibility gaps across multiple beds. Recovery often requires operator intervention or a device restart—actions that themselves consume staff time and may require escalation to biomedical engineering.
• Attack surface and ease: the vulnerability is network‑accessible and low complexity (no authentication, no user interaction). For any CNS‑6201 reachable from a maintenance VLAN, remote vendor management link, or misconfigured hospital network, the risk surface is high.
• Regulatory / compliance exposure: device downtime affecting patient safety or alarm handling can trigger regulatory reporting requirements depending on local rules and may complicate incident investigations. Hospitals should record mitigation choices and impact analysis decisions.

Quantitatively, trackers show the CVSS scores and low EPSS/attack predictions, which reflect that while the vulnerability is straightforward, public exploitation has not yet been observed—so rapid mitigation is still effective. However, the presence of public CVE details and version lists accelerates the time to weaponization unless mitigations are adopted.

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Vendor posture, EOL and policy implications​

NIHON KOHDEN’s public Product Security Portal lists an advisory entry for the CNS‑6201 vulnerability and notes updates to the advisory after initial publication; JVN and the vendor pages also emphasize that the affected versions are no longer supported, and the vendor recommends migration to successor products. That combination — a high‑severity bug in EOL firmware — is one of the most difficult scenarios for healthcare operators because there may be no vendor patch path for the exact impacted device versions.
Implications:

• When a medical device is out of maintenance support, the only fully reliable remediation is replacement with a supported product or upgraded platform that has an available patch.
• Hospitals that cannot immediately replace EOL devices must adopt compensating controls in the network and operational domains to reduce exposure while planning replacement budgets and schedules.

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Recommended mitigations (practical, prioritized)​

For healthcare IT, clinical engineering, and hospital security teams the response should be immediate and layered. The recommendations below follow an operational priority order: contain, detect, recover, and plan replacement.

• Inventory and expose reduction (Immediate)
• Identify every CNS‑6201 in your estates, record the firmware revision, and classify whether the device is reachable from any non‑clinical or vendor networks. Confirm versions against the published affected list.
• Remove any direct Internet exposure. Block public IP access and ensure no NAT/port‑forwarding allows external reachability.
• Network segmentation and access controls (High priority)
• Place all CNS‑6201 units in a dedicated, tightly controlled monitoring VLAN that is separate from corporate, guest, and vendor internet access zones.
• Implement VLAN ACLs / firewall rules to allow only minimal, explicit host‑to‑host flows required for monitoring operations. Deny all other UDP/TCP traffic by default.
• Drop or explicitly filter the UDP ports/protocols that the device exposes to maintenance networks unless they are required and specifically authorized.
• Ingress filtering and packet validation (Compensating)
• Where feasible, apply stateful firewall or DPI/IPS rules that detect malformed UDP packets (or signature patterns once identified) and block them before they reach the device.
• If your facility operates network segmentation appliances or industrialization‑grade firewalls, create an allowlist of known management IPs and disallow any unknown hosts.
• Remote access hardening
• Prohibit direct remote vendor or remote‑maintenance connections unless they are tunneled via a tightly controlled jump host or VPN gateway with multi‑factor authentication and strict endpoint posture checks.
• Use FTPS/SFTP or similar secure channels for vendor maintenance where possible; do not expose the medical device UDP management ports over a VPN endpoint that has broad access.
• Monitoring, logging and detection (Detect)
• Monitor and log all network traffic to the device and generate alerts on repeated UDP packet sizes, anomalous UDP flows, or process crashes on the CNS‑6201 host (if logs are available).
• Employ correlation between alarm server logs and network flows: repeated reboots, abnormal process terminations, or alarm flood conditions should trigger incident response procedures.
• Operational redundancy and clinical workarounds (Availability)
• Ensure bedside monitors and local telemetry continue to provide hospital staff with patient data in the event of central station outage. Confirm alarm escalation policies and redundancy paths (bedside alarms, telemetry, nurse call integration).
• Train staff on manual or local response procedures for central station outages—document how to triage patients until the central station is restored.
• Replacement and lifecycle planning (Long term)
• Accelerate procurement of supported central monitoring platforms and prioritize replacement for devices confirmed to run the vulnerable EOL versions.
• Incorporate cybersecurity lifecycle clauses into future procurements: signed firmware updates, signed packages, an explicit patch and vulnerability disclosure process, and defined EOL timelines.
• Coordination and disclosure (Communication)
• Coordinate with NIHON KOHDEN support or your local sales/biomedical representative for any vendor‑issued advisories or suggested mitigation packages; follow the vendor’s official remediation guidance as it becomes available.

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Step‑by‑step checklist for system owners (an actionable remediation playbook)​

• Immediately inventory all CNS‑6201 units and record firmware revision numbers. Cross‑check against the affected list.
• Remove devices from any network segments that provide broad access; isolate onto a dedicated monitoring VLAN.
• Block inbound UDP traffic to the CNS‑6201 from untrusted subnets and the internet at the firewall.
• Implement IDS/IPS rules to detect anomalous UDP traffic patterns to monitor for exploitation attempts.
• Enable and forward device and central station logs to your SIEM; create alerts for process crashes or repeated device reboots.
• Validate bedside monitoring redundancy and document clinical manual escalation procedures.
• Open a coordinated ticket with the vendor and document vendor guidance; plan device replacement if vendor support is not available or is insufficient.

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Why a DoS in a central station is not “just an IT problem”​

It is tempting to categorize memory‑corruption issues as “technical IT bugs,” but in healthcare settings the consequences are clinical. Central stations aggregate alarms and provide centralized alarm escalation and display that affects situational awareness across nursing staff. Loss of centralized alarms can:

• Increase time to detect physiologic deterioration.
• Force noisy or error‑prone manual workarounds, increasing alarm fatigue.
• Create audit and regulatory exposures if alarm handling fell outside standard procedures during an incident.

Thus remediation is cross‑disciplinary: hospital IT, clinical engineering, nursing leadership, risk and compliance must coordinate to assess patient‑safety risk and select mitigations that do not themselves cause unacceptable clinical impacts.

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Independent corroboration and technical validation​

This vulnerability is tracked by multiple independent national and commercial sources. JVN (Japan Vulnerability Notes) and NVD/CVE entries consolidate the CNA and CVE metadata and list the affected versions and CVSS vectors. Commercial vulnerability trackers (Tenable, CVE aggregators) reproduce the scoring and note the absence of a public exploit at the time of initial disclosure; threat‑intelligence pages and vulnerability databases list the EPSS and exploitation likelihood as low but non‑zero. This cross‑validation supports the central technical claims in the advisory while emphasizing the time‑sensitivity of exploit risk.

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Strengths and weaknesses of the vendor/industry response​

Strengths:

• The vulnerability was coordinated through established disclosure channels (researcher → CNA/JVN → vendor), with public advisories issued and a CVE assigned quickly.
• The vendor lists the advisory on their product security portal and has updated their response page, indicating at least minimal coordination and communication lines for customers.

Risks / shortcomings:

• The affected CNS‑6201 versions are out of support, which limits the vendor’s ability or obligation to provide patches for every impacted revision. That leaves customers to rely on compensating controls or replacement — both of which have cost and operational impacts.
• A lack of an immediate, widely distributed patch or a technical mitigation (e.g., firmware hotfix) increases the burden on hospital CISOs and clinical engineering teams to implement network-level compensations under time pressure.

Given the product lifecycle reality and the severity of the DoS, procurement and clinical decision‑makers should treat device replacement as a prioritized patient-safety mitigation when budget and logistics permit.

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Practical incident response notes for a confirmed exploitation or test​

If you observe device crashes or suspect exploitation:

• Immediately isolate the affected CNS‑6201 from upstream networks while preserving the device for forensic capture (do not power‑cycle if you need volatile memory investigation).
• Collect network captures (pcap) from the monitoring VLAN and correlate timestamps with device logs and central station event logs.
• Engage clinical leadership to confirm fallback alarm coverage and enact documented patient‑safety workarounds.
• Report the incident to national authorities or healthcare cyber‑response agencies as required by regulation and coordinate with NIHON KOHDEN and JPCERT/CC or equivalent.
• If an exploit packet is identified, develop IPS signatures or firewall drop rules to block the specific UDP pattern; however, treat this as temporary and confirm signatures do not disrupt legitimate operations.

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Closing assessment and recommended next steps​

CVE‑2025‑59668 is a high‑impact but narrow class of vulnerability: it does not directly enable data theft or code execution in the published record, yet it enables a remote unauthenticated actor to deny the central monitoring function on affected NIHON KOHDEN CNS‑6201 devices. That availability failure carries real clinical risk, especially in ICUs and multi‑patient monitoring environments.
Actionable priorities for hospitals and device owners:

• Immediately inventory and isolate affected devices; block public/internet access and reduce network reachability to the smallest set of authorized hosts.
• Implement monitoring and packet‑filtering compensations while planning rapid replacement of EOL devices.
• Maintain cross‑disciplinary coordination between IT, clinical engineering and frontline clinical teams to ensure safe fallback procedures are tested and documented.

Finally, treat this advisory as a reminder: medical device security is as much about lifecycle management and procurement policy as it is about software fixes. Devices that are out of support present a chronic, accumulative risk—remediation requires planning, budget, and coordinated operational safeguards to protect patients while technical solutions are engineered or devices replaced.

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Source: CISA NIHON KOHDEN Central Monitor CNS-6201 | CISA