Comprehensive Technical Analysis of EUVD-2025-206576 (CVE-2025-7964)

Zigbee Coordinator Denial-of-Service via Malformed 802.15.4 MAC Data Request

1. Vulnerability Assessment & Severity Evaluation

Vulnerability Overview

EUVD-2025-206576 (CVE-2025-7964) is a high-severity denial-of-service (DoS) vulnerability in the Silicon Labs Zigbee Stack, affecting Zigbee Coordinators and Routers. The flaw arises from improper handling of a malformed 802.15.4 MAC Data Request, which triggers an unintended "network leave" request from the Coordinator to a Zigbee Router. This forces the Router into a non-rejoinable state, disrupting network connectivity for dependent end devices.

CVSS v4.0 Severity Analysis

Metric	Value	Explanation
Base Score	9.2 (Critical)	High impact on availability with low attack complexity.
Attack Vector (AV:N)	Network	Exploitable remotely over Zigbee radio.
Attack Complexity (AC:L)	Low	No specialized conditions required.
Attack Requirements (AT:N)	None	No user interaction or prior access needed.
Privileges Required (PR:N)	None	Unauthenticated exploitation possible.
User Interaction (UI:N)	None	No user action required.
Vulnerable System Confidentiality (VC:N)	None	No data exposure.
Vulnerable System Integrity (VI:N)	None	No integrity impact.
Vulnerable System Availability (VA:H)	High	Complete DoS on affected Router.
Subsequent System Confidentiality (SC:N)	None	No downstream confidentiality impact.
Subsequent System Integrity (SI:N)	None	No downstream integrity impact.
Subsequent System Availability (SA:H)	High	End devices lose connectivity, requiring manual recommissioning.

Key Takeaways:

• Critical severity (9.2) due to high availability impact and low attack complexity.
• No confidentiality or integrity impact, but severe operational disruption in Zigbee networks.
• No authentication required, making it exploitable by any attacker within radio range.

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2. Potential Attack Vectors & Exploitation Methods

Attack Surface

The vulnerability is exploitable via Zigbee radio communication (802.15.4) and does not require physical access. Attackers can:

1. Craft a malformed 802.15.4 MAC Data Request (e.g., with invalid frame control, sequence number, or payload structure).
2. Transmit the malicious packet to a vulnerable Zigbee Coordinator.
3. Trigger the Coordinator to issue a "network leave" command to a targeted Router.
4. Force the Router into a non-rejoinable state, causing a persistent DoS for all dependent end devices.

Exploitation Scenarios

Scenario	Description	Impact
Targeted Router Disruption	Attacker sends malformed packet to a specific Router via the Coordinator.	Isolated Router DoS; end devices lose connectivity.
Network-Wide DoS	Attacker floods the network with malformed requests, targeting multiple Routers.	Widespread Zigbee network outage; manual recovery required.
Stealthy Persistent Attack	Attacker maintains a low-rate attack to avoid detection while keeping Routers offline.	Long-term disruption without immediate detection.
Combination with Other Attacks	Used as a precursor to Zigbee hijacking or replay attacks by forcing devices to rejoin.	Increased risk of unauthorized device pairing.

Exploitation Requirements

• Hardware: A Software-Defined Radio (SDR) (e.g., HackRF, USRP) or a Zigbee-capable device (e.g., CC2531, CC2650).
• Software: Tools like KillerBee, Scapy, or custom Zigbee packet crafting scripts.
• Proximity: Attacker must be within Zigbee radio range (~10-100m, depending on environment).

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3. Affected Systems & Software Versions

Vulnerable Products

The flaw affects Silicon Labs Zigbee Stack implementations in the following versions:

Product	Affected Versions	Fixed Versions
Silicon Labs Zigbee Stack (Legacy)	≤ 4.4.6	4.4.7+ (if available)
Silicon Labs Zigbee Stack (2025)	≤ 2025.6.1	2025.6.2+

Affected Devices

• Zigbee Coordinators (e.g., Silicon Labs EFR32MG, EM35x, JN5189-based gateways).
• Zigbee Routers (e.g., smart plugs, light switches, industrial sensors).
• End devices (e.g., IoT sensors, smart locks) indirectly affected if they rely on a vulnerable Router.

Non-Affected Systems

• Zigbee 3.0+ stacks from other vendors (e.g., Texas Instruments, NXP, Digi).
• Thread or Matter-over-Thread devices (different protocol stack).
• Z-Wave, Bluetooth, or Wi-Fi IoT devices.

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4. Recommended Mitigation Strategies

Immediate Actions

1. Apply Vendor Patches

   • Upgrade to Silicon Labs Zigbee Stack 2025.6.2+ (or the latest available version).
   • If using legacy stacks (≤4.4.6), migrate to a supported version or apply vendor-provided hotfixes.

2. Network Segmentation & Isolation

   • Isolate critical Zigbee Routers from untrusted networks.
   • Disable unnecessary Zigbee Coordinator functions (e.g., remote management) if not required.

3. Radio Frequency (RF) Monitoring & Intrusion Detection

   • Deploy Zigbee intrusion detection systems (IDS) (e.g., Zigbee Sniffer + Wireshark, KillerBee, or commercial solutions).
   • Monitor for unusual "network leave" requests or malformed 802.15.4 packets.

4. Manual Recovery Procedures

   • Document recommissioning steps for affected Routers.
   • Automate rejoin processes where possible to reduce downtime.

Long-Term Mitigations

5. Firmware Hardening

   • Disable automatic "network leave" responses unless explicitly required.
   • Implement rate-limiting for MAC Data Requests to prevent flooding.

6. Network Resilience Improvements

   • Deploy redundant Routers to ensure end devices can rejoin alternative parents.
   • Use Zigbee 3.0+ with improved security (e.g., Trust Center Link Keys, APS Encryption).

7. Vendor & Supply Chain Security

   • Audit third-party Zigbee stacks for similar vulnerabilities.
   • Enforce secure development practices (e.g., fuzz testing, static/dynamic analysis).

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5. Impact on the European Cybersecurity Landscape

Sector-Specific Risks

Sector	Potential Impact	Regulatory Considerations
Smart Homes & Consumer IoT	Disruption of smart lighting, locks, and sensors.	EU Cyber Resilience Act (CRA), GDPR (if personal data is exposed during recommissioning).
Industrial IoT (IIoT)	Downtime in smart factories, logistics, and critical infrastructure.	NIS2 Directive, IEC 62443 (Industrial Cybersecurity).
Healthcare (IoMT)	Failure of medical devices (e.g., patient monitors, infusion pumps).	MDR (Medical Device Regulation), HIPAA-equivalent (GDPR).
Smart Cities	Disruption of smart meters, traffic systems, and environmental sensors.	EU Smart Cities Framework, ENISA Guidelines.
Energy & Utilities	Outages in smart grids and renewable energy monitoring.	EU Critical Entities Resilience Directive (CER).

Broader Implications

• Supply Chain Risks: Silicon Labs is a major Zigbee chipset provider, meaning this vulnerability could affect millions of devices across Europe.
• Compliance Challenges: Organizations may face non-compliance with NIS2, CRA, or sector-specific regulations if they fail to patch.
• Increased Attack Surface: As Zigbee adoption grows in smart cities and Industry 4.0, such vulnerabilities become high-value targets for nation-state and criminal actors.
• Incident Response Burden: Manual recommissioning of devices increases operational costs and extends recovery times.

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6. Technical Details for Security Professionals

Root Cause Analysis

The vulnerability stems from improper input validation in the Zigbee Coordinator’s MAC layer when processing 802.15.4 Data Request frames. Key technical details:

• Malformed Frame Structure: The attack likely involves invalid frame control fields, incorrect sequence numbers, or malformed payloads that trigger an unintended state transition in the Coordinator.
• State Machine Flaw: The Coordinator incorrectly interprets the malformed request as a legitimate command to force a Router to leave the network.
• Non-Rejoinable State: The Router enters a persistent error state where it rejects all rejoin attempts, requiring manual intervention.

Exploitation Proof-of-Concept (PoC) Outline

1. Packet Crafting:
   • Use Scapy or KillerBee to generate a malformed 802.15.4 Data Request.
   • Example (pseudo-code):

     from scapy.all import *
     malformed_frame = RadioTap() / Dot15d4Data(
         dest_panid=0xFFFF,  # Broadcast PAN ID
         dest_addr=0x1234,   # Target Router MAC
         src_addr=0x5678,    # Spoofed Coordinator MAC
         fcf_reserved=0x1,   # Invalid frame control field
         seqnum=0xFF         # Invalid sequence number
     ) / Raw(load="\xAA\xBB\xCC")  # Malformed payload
     sendp(malformed_frame, iface="wlan0", count=1)
     

2. Transmission:
   • Send the packet via SDR or a compromised Zigbee device.
3. Observation:
   • The Coordinator issues a "network leave" command to the Router.
   • The Router stops responding and rejects rejoin requests.

Forensic Indicators

• Network Logs:
  • Unexpected "network leave" requests from the Coordinator.
  • Increased rejoin attempts from end devices.
• Radio Traffic Analysis:
  • Malformed 802.15.4 frames with invalid FCF or sequence numbers.
  • Unusual MAC addresses in Data Requests.

Reverse Engineering & Patch Analysis

• Binary Diffing: Compare vulnerable (≤2025.6.1) vs. patched (2025.6.2+) firmware to identify:
  • Input validation fixes in the MAC layer.
  • State machine corrections to prevent unintended "leave" commands.
• Fuzz Testing: Use AFL, Boofuzz, or custom Zigbee fuzzers to identify similar flaws.

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Conclusion & Recommendations

EUVD-2025-206576 (CVE-2025-7964) represents a critical DoS vulnerability in Silicon Labs Zigbee Stack, with severe operational impacts across consumer, industrial, and critical infrastructure sectors. Given its low attack complexity and high availability impact, organizations must:

1. Patch immediately to the latest Zigbee Stack version.
2. Deploy RF monitoring to detect exploitation attempts.
3. Implement network resilience measures (e.g., redundant Routers).
4. Prepare manual recovery procedures for affected devices.

Failure to mitigate this vulnerability could lead to:

• Prolonged IoT device outages in smart homes, cities, and industries.
• Regulatory non-compliance under NIS2, CRA, and sector-specific laws.
• Increased attack surface for nation-state and criminal threat actors.

Security teams should:

• Monitor vendor advisories for additional patches.
• Conduct penetration testing on Zigbee networks.
• Engage with ENISA and national CSIRTs for coordinated response.

For further details, refer to:

• Silicon Labs Security Advisory
• CVE-2025-7964 Entry
• ENISA IoT Security Guidelines