CVE-2020-35684 in NicheStack
Summary
by MITRE • 08/19/2021
An issue was discovered in HCC Nichestack 3.0. The code that parses TCP packets relies on an unchecked value of the IP payload size (extracted from the IP header) to compute the length of the TCP payload within the TCP checksum computation function. When the IP payload size is set to be smaller than the size of the IP header, the TCP checksum computation function may read out of bounds (a low-impact write-out-of-bounds is also possible).
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Analysis
by VulDB Data Team • 08/21/2021
The vulnerability identified in HCC Nichestack 3.0 represents a critical buffer over-read condition that stems from improper validation of IP header fields during TCP packet processing. This flaw exists within the network stack's packet parsing logic where the system fails to properly validate the relationship between IP header fields and payload dimensions before proceeding with TCP checksum calculations. The issue specifically manifests when an attacker crafts a malicious TCP packet with an IP payload size field that is intentionally smaller than the actual IP header length, creating a scenario where the parsing code attempts to access memory locations beyond the intended buffer boundaries.
The technical implementation of this vulnerability occurs within the TCP checksum computation function where the system assumes that the IP payload size field accurately represents the available data for processing. When this assumption is violated through malformed packet construction, the code proceeds to compute TCP payload lengths based on the manipulated IP payload size value, leading to out-of-bounds memory access patterns. This type of vulnerability falls under the CWE-129 weakness category, which specifically addresses improper validation of array indices and buffer bounds checking in network protocol implementations. The unchecked nature of the IP payload size field creates a direct pathway for memory corruption that can potentially be exploited by remote attackers.
From an operational impact perspective, this vulnerability presents a significant risk to systems running HCC Nichestack 3.0 as it can lead to system instability, application crashes, or potentially more severe consequences if the out-of-bounds access results in data corruption or memory manipulation. The low-impact write-out-of-bounds capability suggests that while immediate system compromise may not be guaranteed, the vulnerability creates opportunities for more sophisticated attack vectors that could be combined with other techniques to achieve unauthorized access or denial of service conditions. Network infrastructure devices and embedded systems utilizing this stack may experience unexpected behavior when processing malformed packets, potentially affecting network availability and data integrity.
The mitigation strategies for this vulnerability should focus on implementing robust input validation mechanisms that verify the relationship between IP header fields before proceeding with packet processing operations. System administrators should prioritize applying vendor-provided patches or updates that address the specific buffer handling logic in the TCP checksum computation function. Additionally, network monitoring solutions should be enhanced to detect and alert on anomalous packet patterns that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper defensive programming practices and adherence to secure coding guidelines that prevent buffer over-read conditions in network protocol implementations. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of exploitation attempts and maintain compliance with cybersecurity frameworks that emphasize secure network stack implementation practices.