Moxa CVE-2002-20001: Resource Exhaustion Vulnerability in Diffie-Hellman Key Exchange Protocol
Act Now3.1MPSA-258261Jun 2, 2025
Summary
A resource exhaustion vulnerability exists in the Diffie-Hellman key exchange protocol (CVE-2002-20001, CWE-400). Remote attackers can send malformed DHE public key values that force servers to perform expensive modular exponentiation calculations. An attacker with minimal resources can require the server to use its largest supported key size, causing significant CPU consumption and service degradation or complete denial of service. The attack does not require authentication and exploits the server's DHE cipher suite implementation. This affects any product or service accepting DHE cipher suites.
What this means
What could happen
An attacker can flood the server with specially crafted DHE key exchange requests, forcing it to perform expensive cryptographic calculations that consume CPU resources and degrade or disable communication services.
Who's at risk
Organizations using Moxa Diffie protocol implementations in network devices, industrial control systems, or communication gateways should prioritize assessment. This affects any ICS device or edge appliance that relies on DHE for encrypted communications.
How it could be exploited
An attacker connects to a device or service using DHE (Diffie-Hellman Ephemeral) cipher suites and sends specially crafted numbers that appear to be DHE public keys but are designed to trigger expensive modular exponentiation calculations on the server side. The attacker can repeat this with large key sizes to maximize CPU impact. This requires no authentication and minimal attacker resources.
Prerequisites
- Device or service must accept DHE cipher suites during TLS/SSL negotiation
- Network connectivity to the affected service
- Client can claim DHE-only communication capabilities
remotely exploitableno authentication requiredlow complexity attackhigh EPSS score (14.7%)denial of service impact on critical communications
Exploitability
High exploit probability (EPSS 14.7%)
Affected products (1)
ProductAffected VersionsFix Status
DiffieAll versionsNo fix yet
Remediation & Mitigation
0/3
Do now
0/1WORKAROUNDDisable DHE cipher suites on the device if not required for operations
Schedule — requires maintenance window
0/1Patching may require device reboot — plan for process interruption
HOTFIXApply vendor fixes for Moxa Diffie product from MOXA MPSA-258261
Long-term hardening
0/1HARDENINGImplement network segmentation to restrict access to management and communication interfaces from untrusted networks
CVEs (1)
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