CVE-2022-20685 flaw in the Modbus preprocessor of the Snort makes it unusable

CVE-2022-20685 flaw in the Modbus preprocessor of the Snort detection engine could trigger a DoS condition and make it ineffective against malicious traffic.

Snort is a free open source network intrusion detection system (IDS) and intrusion prevention system (IPS) which is currently developed by Cisco.

The software performs real-time traffic analysis and packet logging on Internet Protocol (IP) networks, protocol analysis, content searching and matching. The project is also known for its use in attack detection.

Uri Katz, a security researcher at Claroty, detailed a flaw in the Modbus preprocessor of the Snort detection engine, tracked as CVE-2022-20685, that could trigger a DoS condition and make the software ineffective against malicious traffic.

The CVE-2022-20685 vulnerability is an integer-overflow issue that can cause the Snort Modbus OT preprocessor to enter an infinite while-loop.

According to the advisory, the vulnerability can be exploited by a remote attacker. The flaw affects all open-source Snort project releases earlier than 2.9.19 and release 3.1.11.0.

While researching Snort OT preprocessors, we decided to focus on Modbus because it was one of the more complex OT preprocessors Snort supports.

The researchers focused their analysis on Snort OT preprocessor, in particular in Modbus one because Modbus is a popular industrial protocol.

“An integer overflow vulnerability in the Snort Modbus OT preprocessor enables an attacker to remotely send a crafted packet to a vulnerable system, triggering an infinite while-loop and creating a denial-of-service condition.” reads the analysis published by Claroty that includes technical details about the issue.

“A vulnerability in the Modbus preprocessor of the Snort detection engine could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.” reads the security advisory published by Cisco. “This vulnerability is due to an integer overflow while processing Modbus traffic. An attacker could exploit this vulnerability by sending crafted Modbus traffic through an affected device. A successful exploit could allow the attacker to cause the Snort process to hang, causing traffic inspection to stop.”

The researchers pointed out that successful exploitation of this vulnerability can have devastating impacts on enterprise and OT networks.

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Pierluigi Paganini

(SecurityAffairs – hacking, DoS)

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Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.