CVE-2020-5209 in NetHack
Summary
by MITRE
In NetHack before 3.6.5, unknown options starting with -de and -i can cause a buffer overflow resulting in a crash or remote code execution/privilege escalation. This vulnerability affects systems that have NetHack installed suid/sgid and shared systems that allow users to influence command line options. Users should upgrade to NetHack 3.6.5.
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Analysis
by VulDB Data Team • 03/27/2024
The vulnerability identified as CVE-2020-5209 represents a critical buffer overflow issue within the NetHack game engine that affects versions prior to 3.6.5. This flaw manifests when the game processes command line options that begin with specific prefixes including -de and -i, creating a scenario where malicious input can exceed allocated memory buffers and potentially lead to arbitrary code execution. The vulnerability is particularly concerning due to NetHack's widespread installation on systems where it operates with elevated privileges through suid/sgid permissions, making it a prime target for privilege escalation attacks. The buffer overflow occurs during the parsing of these unknown command line options, where insufficient input validation allows attackers to craft malicious arguments that overwrite adjacent memory regions.
The technical implementation of this vulnerability stems from inadequate bounds checking within the command line argument parsing mechanism of NetHack. When the game encounters options starting with -de or -i, it fails to properly validate the length of these arguments before copying them into fixed-size buffers. This classic buffer overflow condition, classified under CWE-121, allows attackers to overwrite critical memory locations including return addresses and control flow information. The vulnerability's exploitation potential is significantly amplified when NetHack is installed with suid/sgid permissions, as demonstrated in the ATT&CK framework's privilege escalation techniques where attackers leverage programs with elevated privileges to gain unauthorized access to system resources. The specific nature of the affected options suggests that the parsing logic does not adequately handle variable-length input that exceeds predetermined buffer limits.
The operational impact of CVE-2020-5209 extends beyond simple game crashes to encompass serious security implications for system integrity and user safety. On systems where NetHack runs with elevated privileges, successful exploitation could enable attackers to execute arbitrary code with the privileges of the game process, potentially leading to complete system compromise. This risk is particularly severe in shared computing environments where multiple users have access to command line interfaces that can influence how NetHack is invoked. The vulnerability affects not only individual user systems but also multi-user environments such as university networks, shared servers, and cloud infrastructure where NetHack installations might be present. Organizations running these vulnerable versions face potential data breaches, unauthorized privilege escalation, and system-wide compromise scenarios that could affect multiple users and applications within the same environment.
Mitigation strategies for CVE-2020-5209 primarily focus on immediate patching to NetHack version 3.6.5, which contains the necessary code modifications to properly validate command line arguments and prevent buffer overflow conditions. System administrators should prioritize updating all NetHack installations, particularly those configured with suid/sgid permissions, to eliminate the attack surface. Additional defensive measures include implementing strict input validation for all command line arguments, monitoring for unusual command line patterns, and reviewing system configurations to ensure that NetHack is not running with unnecessary elevated privileges. The vulnerability highlights the importance of proper input validation and memory management practices in software development, aligning with security best practices outlined in the OWASP Top Ten and other industry standards. Organizations should also consider implementing network segmentation and access controls to limit potential exploitation vectors and reduce the overall impact of such vulnerabilities in their infrastructure.