OTPulse

Moxa Security Enhancement: SSL Medium Strength Cipher Suites Supported (SWEET32)

Act NowMPSA-251371Oct 9, 2025
Moxa
Summary

Moxa devices support DES and Triple DES cipher suites in TLS, SSH, and IPSec protocols. These ciphers have a birthday bound of approximately four billion blocks, making it feasible for remote attackers to decrypt long-duration encrypted sessions through a birthday attack, particularly HTTPS sessions using Triple DES in CBC mode (CVE-2016-2183, also known as SWEET32). Moxa has no planned fixes for this issue; users must implement compensating controls such as disabling weak ciphers and restricting network access to management interfaces.

What this means
What could happen
An attacker able to capture encrypted traffic between your device and users or connected systems could potentially decrypt it by exploiting weaknesses in older DES/Triple DES encryption. This could expose sensitive configuration data, authentication credentials, or operational commands sent over encrypted connections.
Who's at risk
This affects any organization running Moxa industrial devices (industrial Ethernet switches, serial device servers, gateways, or communication modules) that handle encrypted management traffic or sensitive protocol data. This is relevant to water utilities, electric utilities, and manufacturing facilities that rely on Moxa devices for network connectivity and control system communication.
How it could be exploited
An attacker positioned on the network path between a Moxa device and a client (network sniffing) captures encrypted TLS/SSH sessions using weak DES or Triple DES ciphers. Over days or weeks of capturing encrypted blocks from the same session, they exploit a birthday attack vulnerability to recover plaintext data, potentially including credentials or sensitive commands.
Prerequisites
  • Network ability to capture encrypted traffic between the Moxa device and connected clients (e.g., man-in-the-middle position or network sniffing)
  • Long-duration encrypted session using DES or Triple DES cipher suite (hours or days of continuous encryption)
  • Moxa device configured to accept medium-strength ciphers
remotely exploitableno patch availableaffects encrypted management channelslong-duration attack (hours to weeks)
Exploitability
Likely to be exploited — EPSS score 37.8%
Public Proof-of-Concept (PoC) on GitHub (1 repository)
Affected products (1)
ProductAffected VersionsFix Status
Security Enhancement: SSL Medium Strength Cipher Suites Supported (SWEET32)All versionsNo fix (EOL)
Remediation & Mitigation
0/4
Do now
0/2
HARDENINGDisable DES and Triple DES cipher suites in the Moxa device security settings; configure to use only strong ciphers (AES-128 or higher)
WORKAROUNDRestrict network access to management ports (SSH, HTTPS) using firewall rules to trusted engineering workstations or maintenance networks only
Schedule — requires maintenance window
0/1

Patching may require device reboot — plan for process interruption

HARDENINGReview and update TLS/SSH client configurations connecting to the Moxa device to enforce strong cipher suites, rejecting weak ciphers
Mitigations - no patch available
0/1
Security Enhancement: SSL Medium Strength Cipher Suites Supported (SWEET32) has reached End of Life. The vendor will not release a patch. Apply the following compensating controls:
HARDENINGImplement network segmentation to isolate the Moxa device on a dedicated OT network segment with restricted lateral access
View full Moxa Security advisory
API: /api/v1/advisories/d1417c7d-473c-40f1-a6c4-55a1885445a8

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Moxa Security Enhancement: SSL Medium Strength Cipher Suites Supported (SWEET32) - OTPulse