CVE-2018-16951 in xunfeng
Summary
by MITRE
xunfeng 0.2.0 allows command execution via CSRF because masscan.py mishandles backquote characters, a related issue to CVE-2018-16832.
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Analysis
by VulDB Data Team • 05/16/2023
The vulnerability identified as CVE-2018-16951 affects the xunfeng 0.2.0 network scanning tool, representing a critical security flaw that enables arbitrary command execution through cross-site request forgery attacks. This vulnerability stems from improper handling of backquote characters within the masscan.py component, creating a dangerous condition where user-supplied input can be interpreted as shell commands rather than mere data. The flaw directly relates to CVE-2018-16832, indicating a pattern of similar input sanitization issues within the xunfeng framework that collectively undermine the tool's security posture.
The technical implementation of this vulnerability occurs when the masscan.py script processes user input containing backquote characters without proper sanitization or escaping mechanisms. Backquotes in shell contexts are interpreted as command substitution operators, meaning any content enclosed within backquotes gets executed as shell commands. When an attacker crafts a malicious request containing backquote characters in parameters that are passed to masscan.py, the script fails to properly escape or validate these inputs before using them in shell operations. This creates a classic command injection vulnerability that can be exploited through CSRF attacks, where an attacker tricks a victim into making requests to the vulnerable xunfeng application that execute malicious commands on the server.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it allows attackers to execute arbitrary commands with the privileges of the xunfeng service account. This could potentially lead to complete system compromise, data exfiltration, or the establishment of persistent backdoors. The vulnerability is particularly dangerous because it combines multiple attack vectors - the CSRF mechanism allows for automated exploitation without user interaction, while the command execution capability provides broad attack surface. Organizations using xunfeng 0.2.0 for network scanning operations face significant risk, especially in environments where the tool is accessible to untrusted users or when deployed in web interfaces that do not properly validate user input.
Security mitigations for CVE-2018-16951 should focus on implementing proper input validation and sanitization measures within the masscan.py component. The most effective approach involves escaping or removing special shell characters from user input before processing, particularly backquote characters, dollar signs, and other shell metacharacters that could enable command substitution. Organizations should also implement proper CSRF protection mechanisms including secure token validation, origin checking, and proper session management to prevent unauthorized request execution. Additionally, following the principle of least privilege by running the xunfeng service with minimal required permissions and implementing network segmentation can limit the potential damage from successful exploitation. This vulnerability aligns with CWE-78, which specifically addresses improper neutralization of special elements used in OS commands, and relates to ATT&CK technique T1059.001 for command and scripting interpreter, highlighting the importance of proper input validation and secure coding practices in preventing such critical vulnerabilities.
The vulnerability demonstrates the critical importance of input validation in security-sensitive applications, particularly those involving system command execution. It underscores the need for developers to implement robust sanitization routines and avoid direct shell command construction from user-supplied data. Organizations should prioritize updating to patched versions of xunfeng or implementing compensating controls until remediation is complete. This vulnerability serves as a reminder that seemingly minor input handling flaws can create catastrophic security implications, particularly when combined with other attack vectors like CSRF that can automate exploitation. The relationship to CVE-2018-16832 indicates that the xunfeng project requires comprehensive security auditing and input validation improvements across its entire codebase to prevent similar vulnerabilities from occurring in other components.