CVE-2020-27737 in Nucleus NET
Summary
by MITRE • 04/23/2021
A vulnerability has been identified in Nucleus 4 (All versions < V4.1.0), Nucleus NET (All versions), Nucleus RTOS (versions including affected DNS modules), Nucleus ReadyStart (All versions < V2017.02.3), Nucleus Source Code (versions including affected DNS modules), SIMOTICS CONNECT 400 (All versions < V0.5.0.0), VSTAR (versions including affected DNS modules). The DNS response parsing functionality does not properly validate various length and counts of the records. The parsing of malformed responses could result in a read past the end of an allocated structure. An attacker with a privileged position in the network could leverage this vulnerability to cause a denial-of-service condition or leak the memory past the allocated structure.
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Analysis
by VulDB Data Team • 04/27/2021
This vulnerability resides within the DNS response parsing functionality of multiple Nucleus products including Nucleus 4, Nucleus NET, Nucleus RTOS, Nucleus ReadyStart, Nucleus Source Code, SIMOTICS CONNECT 400, and VSTAR systems. The flaw manifests in the improper validation of length and count parameters within DNS records during response processing. According to CWE-129, this represents an implementation weakness where insufficient validation of input data leads to buffer over-read conditions. The vulnerability specifically affects versions prior to V4.1.0 for Nucleus 4, all versions of Nucleus NET, Nucleus RTOS with affected DNS modules, all versions of Nucleus ReadyStart prior to V2017.02.3, and all versions of SIMOTICS CONNECT 400 before V0.5.0.0, along with affected versions of VSTAR.
The technical exploitation of this vulnerability occurs when malformed DNS responses are processed by the affected systems. When the DNS parsing code encounters records with invalid length or count fields, it fails to properly validate these parameters before attempting to access memory structures. This leads to a read past the end of an allocated buffer, which constitutes a classic buffer over-read condition. The memory access violation can result in system instability, causing denial-of-service conditions that disrupt normal operations. From an operational perspective, this vulnerability represents a significant risk for industrial control systems and embedded devices that rely on DNS resolution for network communication.
The attack vector requires an attacker to possess a privileged network position to inject malformed DNS responses into the network traffic. This aligns with ATT&CK technique T1071.004 for application layer protocol: DNS, where adversaries manipulate DNS responses to achieve their objectives. The impact extends beyond simple service disruption to include potential memory disclosure, which could expose sensitive system information to attackers. This memory leakage could reveal critical data such as system pointers, credentials, or other confidential information stored in memory. The vulnerability affects both networked embedded systems and industrial automation environments where these Nucleus products are deployed, potentially compromising the integrity of critical infrastructure operations.
Mitigation strategies should focus on immediate software updates to versions V4.1.0 or later for Nucleus 4, V2017.02.3 or later for Nucleus ReadyStart, and V0.5.0.0 or later for SIMOTICS CONNECT 400. Organizations should also implement network segmentation and DNS monitoring to detect and prevent malformed DNS responses from reaching affected systems. Additionally, network administrators should consider implementing DNS response validation mechanisms and monitoring for unusual DNS traffic patterns that could indicate exploitation attempts. The vulnerability highlights the importance of input validation in embedded systems and underscores the need for robust security practices in industrial control environments where system reliability and security are paramount.