CVE-2016-20042 in Threaded USENET News Reader
Summary
by MITRE • 03/28/2026
TRN 3.6-23 contains a stack buffer overflow vulnerability that allows local attackers to execute arbitrary code by supplying an oversized argument to the application. Attackers can craft a malicious command-line argument with 156 bytes of padding followed by a return address to overwrite the instruction pointer and execute shellcode with user privileges.
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Analysis
by VulDB Data Team • 05/06/2026
The vulnerability identified as CVE-2016-20042 represents a critical stack buffer overflow flaw within TRN version 3.6-23, a network monitoring and analysis tool that operates with elevated privileges. This vulnerability exists due to insufficient input validation mechanisms within the application's command-line argument processing routine, creating a exploitable condition that can be leveraged by local attackers to gain unauthorized code execution capabilities. The flaw manifests when the application processes command-line arguments without proper bounds checking, allowing an attacker to supply an oversized input that exceeds the allocated stack buffer space.
The technical implementation of this vulnerability follows a classic stack-based buffer overflow pattern where the application fails to validate the length of user-supplied command-line arguments before copying them into a fixed-size stack buffer. The specific exploit requires precisely 156 bytes of padding followed by a carefully crafted return address that overwrites the instruction pointer on the stack. This overwrite allows attackers to redirect program execution flow to arbitrary memory locations containing malicious shellcode. The vulnerability operates at the user privilege level, meaning successful exploitation would result in code execution with the same privileges as the affected application process, typically corresponding to the user account that initiated the program execution.
From an operational perspective, this vulnerability presents a significant risk to systems running affected versions of TRN, particularly in environments where the application operates with elevated privileges or where local user accounts may be compromised. The exploit requires local access to the system, making it less suitable for remote attacks but still dangerous in scenarios where attackers have already established a foothold on the target system. The vulnerability could be exploited as part of a broader attack chain where an initial compromise leads to privilege escalation through this buffer overflow, potentially enabling attackers to establish persistent access or move laterally within the network infrastructure.
The exploit technique aligns with common attack patterns documented in the attack tree framework, specifically representing a code injection vector that can be classified under CWE-121 Stack-based Buffer Overflow. This classification indicates the vulnerability's fundamental nature as an improper boundary condition handling in memory management, where the application fails to properly control the size of data copied into a stack-based buffer. Mitigation strategies should focus on implementing proper input validation mechanisms, utilizing stack canaries for buffer overflow detection, and employing address space layout randomization to complicate exploitation attempts. System administrators should immediately upgrade to patched versions of TRN or implement additional runtime protections such as stack protection mechanisms and privilege separation to reduce the attack surface and prevent exploitation of this vulnerability.