CVE-2022-41716 in Google
Summary
by MITRE • 11/02/2022
Due to unsanitized NUL values, attackers may be able to maliciously set environment variables on Windows. In syscall.StartProcess and os/exec.Cmd, invalid environment variable values containing NUL values are not properly checked for. A malicious environment variable value can exploit this behavior to set a value for a different environment variable. For example, the environment variable string "A=B\x00C=D" sets the variables "A=B" and "C=D".
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Analysis
by VulDB Data Team • 10/30/2024
This vulnerability exists in the go programming language's handling of environment variables within the syscall.StartProcess and os/exec.Cmd functions on windows systems. The core issue stems from inadequate input validation where null byte characters are not properly sanitized from environment variable values, creating a potential vector for environment variable manipulation. The vulnerability is classified under CWE-772 which deals with improper handling of null bytes in environment variables, representing a fundamental flaw in how the runtime environment processes variable assignments. When a malicious actor injects null bytes into environment variable values, the system's parsing mechanism interprets these null characters as delimiters, effectively allowing attackers to manipulate multiple environment variables through a single malicious input.
The technical exploitation occurs because the go runtime does not validate the presence of null bytes within environment variable values before processing them. When the system encounters a null byte within an environment variable string such as "A=BC=D", it treats the null byte as a termination character, causing the parser to split the string at that point. This results in the first portion "A=B" being treated as one variable and the second portion "C=D" being treated as another variable, effectively allowing attackers to bypass normal variable assignment restrictions. The vulnerability specifically affects windows platforms where the environment variable parsing behavior differs from unix-like systems, making it particularly dangerous in cross-platform applications that may run on both systems. This behavior aligns with ATT&CK technique T1059.001 which involves executing malicious code through command-line interfaces, and T1556.002 which covers credential access through environment variable manipulation.
The operational impact of this vulnerability is significant as it can enable attackers to manipulate critical system variables, potentially leading to privilege escalation, code injection, or information disclosure. Attackers could exploit this to inject malicious environment variables that influence application behavior, redirect system calls, or manipulate application configuration. The vulnerability is particularly concerning in applications that accept user input for environment variables or those that process untrusted data through the os/exec package. Systems running vulnerable go applications are at risk of environment variable poisoning attacks, where attackers can manipulate the runtime environment of applications to execute unintended behavior. This vulnerability affects the fundamental security model of applications that rely on environment variables for configuration and can lead to cascading security issues throughout the system.
Mitigation strategies should focus on implementing proper input validation and sanitization of environment variable values before processing them through the go runtime. Developers should avoid using user-controlled input directly in environment variable assignments and implement strict validation mechanisms to reject null byte characters. The recommended approach includes sanitizing environment variable values by removing or encoding null bytes before passing them to syscall.StartProcess or os/exec.Cmd functions. Additionally, applications should implement proper error handling and logging to detect anomalous environment variable patterns that may indicate exploitation attempts. System administrators should ensure that all go applications are updated to versions that address this vulnerability, and should consider implementing monitoring solutions that can detect suspicious environment variable manipulation patterns. Organizations should also review their application code to identify any potential usage of vulnerable functions and implement defensive programming practices to prevent null byte injection attacks.