CVE-2017-17790 in Ruby
Summary
by MITRE
The lazy_initialize function in lib/resolv.rb in Ruby through 2.4.3 uses Kernel#open, which might allow Command Injection attacks, as demonstrated by a Resolv::Hosts::new argument beginning with a '|' character, a different vulnerability than CVE-2017-17405. NOTE: situations with untrusted input may be highly unlikely.
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Analysis
by VulDB Data Team • 01/18/2023
The vulnerability identified as CVE-2017-17790 represents a command injection flaw within the Ruby programming language's resolver library, specifically affecting versions through 2.4.3. This security issue resides in the lazy_initialize function located within lib/resolv.rb, where the implementation leverages Kernel#open for handling certain operations. The flaw becomes exploitable when malicious input is passed through Resolv::Hosts::new arguments that begin with the pipe character '|', which in Unix-like systems signals the execution of commands through shell interpretation. This particular vulnerability operates distinct from CVE-2017-17405, indicating a separate attack vector within the same software component. The technical implementation demonstrates how Ruby's resolver system fails to properly sanitize input parameters before processing them through kernel-level open operations that can inadvertently execute shell commands.
The operational impact of this vulnerability extends beyond simple code execution, as it allows attackers to potentially inject and execute arbitrary shell commands on systems running vulnerable Ruby versions. When a Resolv::Hosts::new call receives input starting with '|', the underlying system interprets this as a command to be executed rather than a simple hostname or IP address lookup. This creates a dangerous scenario where untrusted input can be transformed into system command execution, potentially allowing attackers to gain unauthorized access to system resources, execute malicious payloads, or perform reconnaissance activities. The vulnerability's exploitation requires specific conditions where the input flows through the resolver mechanism, making it particularly relevant in applications that process external DNS or host resolution data without proper input validation.
From a security standards perspective, this vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and represents a classic command injection attack vector. The ATT&CK framework categorizes this under T1059.001 for command and scripting interpreter, specifically shell scripting, where adversaries leverage system command execution capabilities to achieve their objectives. The vulnerability's low likelihood of occurring in real-world scenarios stems from the specific input conditions required, but its potential impact remains significant given that Ruby applications often process untrusted network data through resolver functions. The fact that this vulnerability is distinct from CVE-2017-17405 indicates that multiple command injection vectors exist within the same Ruby resolver library, emphasizing the need for comprehensive input validation throughout the codebase. Organizations should prioritize updating to patched Ruby versions and implementing proper input sanitization measures to prevent exploitation of this and similar vulnerabilities in their applications.