CVE-2021-4479 Overview
CVE-2021-4479 affects Dräger Atlan A350 anesthesia workstation software versions 1.00 through 1.01. The vulnerability is an improper input handling flaw [CWE-1286] in the Medibus interface. Attackers can transmit non-Medibus-compliant data to overload the internal processor. The condition develops gradually over several hours, producing loss of data transmission, delayed display of real-time curves, and deviation between displayed airway pressure values and screen curves. The flaw degrades the operational reliability of a clinical device used during anesthesia delivery.
Critical Impact
Crafted malformed Medibus traffic can degrade anesthesia workstation operation, producing inaccurate airway pressure displays and delayed real-time curve rendering during patient care.
Affected Products
- Dräger Atlan A350 software version 1.00
- Dräger Atlan A350 software version 1.01
- Devices exposing the Medibus interface to untrusted serial or networked peers
Discovery Timeline
- 2026-06-02 - CVE-2021-4479 published to the National Vulnerability Database
- 2026-06-03 - Last updated in NVD database
Technical Details for CVE-2021-4479
Vulnerability Analysis
The Dräger Atlan A350 is an anesthesia workstation that exchanges device parameters over the Medibus protocol. Medibus is a serial communication protocol used across Dräger medical devices for telemetry and command exchange. The vulnerability stems from inadequate validation of inbound frames on the Medibus interface. Software versions 1.00 and 1.01 accept malformed, non-compliant data and route it to the internal processor for handling.
Processing this malformed input consumes processor resources without producing useful work. Sustained transmission causes resource pressure to accumulate over hours. The device does not detect or shed the abusive traffic, so degradation progresses while the workstation remains operational.
Observed effects include loss of data transmission through the Medibus link, delayed rendering of real-time waveforms, and divergence between displayed airway pressure numerics and the corresponding screen curves. In a clinical context, those discrepancies can mislead operators monitoring ventilation parameters.
Root Cause
The root cause is improper handling of exceptional conditions at the Medibus protocol parser [CWE-1286]. The parser does not reject or rate-limit frames that violate the Medibus specification. Each malformed frame still incurs processing cost on the internal controller, allowing an attacker to convert malformed input into sustained resource consumption.
Attack Vector
The attack requires reachability to the Medibus interface of the target workstation. An attacker connected to the Medibus link transmits a continuous stream of crafted non-compliant frames. No authentication or user interaction is required. Exploitation does not yield code execution or data disclosure; impact is limited to availability and the integrity of displayed real-time data.
No verified public proof-of-concept code is available. The vulnerability mechanism is described in the Draeger Security Advisory PSA-21-124-1 and the VulnCheck Advisory for Dräger Atlan A350.
Detection Methods for CVE-2021-4479
Indicators of Compromise
- Sustained inbound traffic on the Medibus interface containing frames that fail Medibus protocol validation
- Operator-reported loss of data transmission on the Atlan A350 Medibus link
- Delayed rendering of real-time waveforms or visible lag between numeric and graphical displays
- Deviation between displayed airway pressure values and the corresponding curves on screen
Detection Strategies
- Monitor Medibus serial or gateway traffic for frames violating the Medibus framing and checksum rules
- Baseline normal Medibus throughput per device and alert on prolonged elevated frame rates
- Correlate device-side event logs with network or serial capture data for the same time window
Monitoring Recommendations
- Capture Medibus traffic at gateway points using a passive tap to preserve clinical traffic integrity
- Track interface error counters and processor utilization metrics exposed by the workstation
- Forward biomedical device logs to a centralized log platform for retention and correlation
How to Mitigate CVE-2021-4479
Immediate Actions Required
- Inventory all Atlan A350 workstations and identify units running software versions 1.00 or 1.01
- Restrict physical and network access to the Medibus interface to authorized clinical equipment only
- Coordinate with Dräger service representatives to schedule the firmware update referenced in PSA-21-124-1
- Brief clinical staff to verify airway pressure values against alternate monitoring sources if Medibus anomalies are observed
Patch Information
Dräger addresses the issue in software releases following version 1.01. Refer to the Draeger Security Advisory PSA-21-124-1 for the corrected version and authorized update procedure. Firmware updates for medical devices must be applied by qualified service personnel in accordance with the manufacturer's instructions.
Workarounds
- Isolate Medibus cabling to direct, point-to-point connections with trusted peripherals
- Disconnect Medibus interfaces that are not required for clinical workflow
- Place biomedical device network segments behind firewalls that block unauthorized hosts from reaching Medibus gateways
- Increase manual verification of displayed parameters during procedures until patched firmware is deployed
# Example: restrict a biomedical VLAN gateway to known Medibus peer addresses
iptables -A FORWARD -i medibus0 -s 10.20.30.0/28 -j ACCEPT
iptables -A FORWARD -i medibus0 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
