CVE-2024-5800: B&R Automation Runtime SSL/TLS Vulnerability

CVE-2024-5800 Overview

CVE-2024-5800 is a cryptographic weakness in the SSL/TLS stack of B&R Automation Runtime versions before 6.0.2. The stack negotiates Diffie-Hellman (DH) key exchange groups with insufficient strength. A network-positioned attacker can capture the resulting SSL/TLS traffic and derive the session key, decrypting confidential communication between the runtime and its clients. The issue is tracked under CWE-326: Inadequate Encryption Strength and affects industrial control systems relying on B&R Automation Runtime for operator, engineering, and machine-to-machine traffic.

Critical Impact
Attackers on the network path can decrypt SSL/TLS sessions and expose credentials, control commands, and process data exchanged with B&R Automation Runtime.

Affected Products

B&R Automation Runtime versions prior to 6.0.2
Industrial controllers and PLCs shipping the affected runtime
Engineering workstations and HMIs communicating with the affected runtime over TLS

Discovery Timeline

2024-08-12 - CVE-2024-5800 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-5800

Vulnerability Analysis

The SSL/TLS stack in B&R Automation Runtime offers Diffie-Hellman key exchange using groups whose modulus size or parameter selection does not meet current cryptographic strength requirements. When a client negotiates a DH or DHE cipher suite, the server-supplied parameters produce a shared secret that can be recovered with feasible computational effort. Once the shared secret is recovered, the attacker derives the session keys and decrypts recorded traffic offline or in near real time.

The flaw is a passive-friendly cryptographic weakness. An attacker does not need to modify traffic to succeed. Capturing the TLS handshake and the encrypted records is sufficient. The confidentiality guarantees of the channel collapse while integrity and availability remain untouched, which aligns with the CWE-326 classification of inadequate encryption strength.

Root Cause

The root cause is the use of DH groups with insufficient key length or weak, well-known parameters in the TLS negotiation defaults. Modern guidance requires DH groups of at least 2048 bits and preferably named groups from RFC 7919 or ECDHE. The affected runtime versions do not enforce these thresholds, allowing negotiation of parameters that fall short of the effective security level expected of TLS.

Attack Vector

Exploitation requires network access to the TLS channel between a client and the B&R Automation Runtime service. Typical attack positions include a compromised switch, a rogue device on the OT/IT boundary, a mirrored port, or any adversary-in-the-middle placement. The attacker records the handshake and ciphertext, then performs the discrete logarithm computation against the negotiated DH group to recover the pre-master secret. No user interaction is needed and no credentials are required to observe traffic. The vulnerability describes traffic decryption in prose; no verified public exploit code is available. See the B&R Automation Security Advisory for vendor technical detail.

Detection Methods for CVE-2024-5800

Indicators of Compromise

TLS handshakes with B&R Automation Runtime endpoints negotiating DHE cipher suites using groups smaller than 2048 bits.
Unexpected passive network taps, SPAN sessions, or ARP anomalies on segments carrying Automation Runtime traffic.
Presence of legacy TLS_DHE_* cipher suites in server hello messages from Automation Runtime hosts still on versions prior to 6.0.2.

Detection Strategies

Inventory B&R Automation Runtime instances and record their versions, flagging any build below 6.0.2.
Use a TLS scanner such as sslscan, testssl.sh, or nmap --script ssl-dh-params against Automation Runtime endpoints to enumerate DH group sizes and cipher suites.
Correlate cipher suite telemetry with OT asset inventories in a SIEM to identify systems negotiating weak DH parameters.

Monitoring Recommendations

Ingest TLS metadata from network sensors (Zeek ssl.log, firewall TLS inspection logs) into a centralized data lake for continuous cipher hygiene checks.
Alert on any DHE handshake using groups below 2048 bits reaching or originating from OT subnets.
Monitor for unauthorized packet capture tooling, promiscuous interfaces, and unexpected east-west traffic in industrial network segments.

How to Mitigate CVE-2024-5800

Immediate Actions Required

Upgrade all B&R Automation Runtime instances to version 6.0.2 or later as specified in the vendor advisory.
Restrict network access to Automation Runtime services to trusted engineering and HMI hosts using firewalls or OT segmentation.
Rotate credentials, certificates, and any secrets that may have transited affected TLS sessions before patching.

Patch Information

B&R Industrial Automation has released Automation Runtime 6.0.2, which corrects the Diffie-Hellman parameter selection in the SSL/TLS stack. Refer to the B&R Automation Security Advisory SA24P011 for fixed versions, upgrade instructions, and compatibility notes for controller hardware.

Workarounds

Where immediate patching is not feasible, tunnel Automation Runtime traffic through an IPsec or WireGuard VPN that enforces strong key exchange.
Place affected devices behind an OT firewall configured to allow only whitelisted management stations, reducing the pool of hosts able to initiate TLS sessions.
Disable or block legacy DHE cipher suites at any TLS terminating proxy in front of the runtime, forcing clients to use stronger negotiated parameters when supported.

bash

# Example: enumerate DH parameters exposed by an Automation Runtime endpoint
nmap --script ssl-enum-ciphers,ssl-dh-params -p 443 <automation-runtime-host>

# Example: quick cipher and DH group audit with testssl.sh
testssl.sh --protocols --fs <automation-runtime-host>:443