CVE-2020-27009 in Nucleus NET
Summary
by MITRE • 04/23/2021
A vulnerability has been identified in Nucleus NET (All versions < V5.2), Nucleus RTOS (versions including affected DNS modules), Nucleus Source Code (versions including affected DNS modules), VSTAR (versions including affected DNS modules). The DNS domain name record decompression functionality does not properly validate the pointer offset values. The parsing of malformed responses could result in a write past the end of an allocated structure. An attacker with a privileged position in the network could leverage this vulnerability to execute code in the context of the current process or cause a denial-of-service condition.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 04/27/2021
This vulnerability resides within the DNS domain name record decompression functionality of several Nucleus products including Nucleus NET, Nucleus RTOS, Nucleus Source Code, and VSTAR systems. The flaw specifically affects versions prior to V5.2 and manifests in the handling of pointer offset values during DNS response parsing. The technical implementation fails to properly validate these pointer offsets, creating a condition where malformed DNS responses can trigger memory corruption. This represents a classic buffer overflow vulnerability that falls under CWE-121, which deals with stack-based buffer overflow conditions, and more specifically CWE-787, which addresses out-of-bounds write vulnerabilities. The vulnerability operates at the network protocol parsing layer where DNS responses are processed, making it particularly dangerous as it can be exploited through network-based attacks.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions to potentially enable remote code execution. When an attacker crafts a malicious DNS response with malformed pointer offsets, the system's DNS parser attempts to follow these invalid pointers, resulting in memory writes that extend beyond the bounds of allocated data structures. This memory corruption can lead to unpredictable behavior including system crashes, application termination, or in more severe cases, arbitrary code execution within the context of the running process. The requirement for a privileged network position indicates this vulnerability is exploitable in scenarios where an attacker can intercept or inject DNS traffic, aligning with ATT&CK technique T1071.004 for application layer protocol tunneling and potentially T1059 for command and control communication.
The exploitation of this vulnerability demonstrates the critical importance of proper input validation in network protocol implementations. The affected systems process DNS responses without adequate bounds checking on pointer offset values, creating a pathway for attackers to manipulate memory layout and potentially gain elevated privileges. This vulnerability highlights the need for robust defensive programming practices including bounds checking, pointer validation, and memory safety mechanisms. Organizations should prioritize immediate remediation through firmware or software updates to V5.2 or later versions that contain proper pointer offset validation. Additional mitigations include network segmentation to limit exposure, DNS filtering to block suspicious responses, and implementing intrusion detection systems to monitor for anomalous DNS traffic patterns. The vulnerability also underscores the importance of secure coding practices and regular security assessments of embedded systems and real-time operating systems where such memory corruption issues can have severe operational consequences.