CVE-2013-1948 in md2pdf
Summary
by MITRE
converter.rb in the md2pdf gem 0.0.1 for Ruby allows context-dependent attackers to execute arbitrary commands via shell metacharacters in a filename.
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Analysis
by VulDB Data Team • 03/24/2015
The vulnerability identified as CVE-2013-1948 affects the md2pdf gem version 0.0.1 in Ruby environments, representing a critical command injection flaw that enables attackers to execute arbitrary system commands through manipulated filename inputs. This vulnerability exists within the converter.rb component of the gem, which processes markdown files and converts them to pdf format. The flaw arises from insufficient input validation and improper sanitization of user-supplied filenames, creating a pathway for malicious actors to inject shell metacharacters that get interpreted by the underlying system shell during the conversion process.
The technical implementation of this vulnerability stems from the gem's failure to properly escape or filter special shell characters such as semicolons, ampersands, backticks, and pipes that are commonly used in command injection attacks. When a user provides a filename containing these metacharacters, the md2pdf gem passes this unvalidated input directly to shell commands without proper sanitization, allowing attackers to chain additional commands that execute with the privileges of the user running the conversion process. This represents a classic command injection vulnerability that aligns with CWE-78, which specifically addresses improper neutralization of special elements used in OS commands, and falls under the broader category of CWE-94, concerning the execution of arbitrary code or commands.
The operational impact of this vulnerability extends beyond simple command execution, as it can enable attackers to perform a wide range of malicious activities including but not limited to data exfiltration, system reconnaissance, privilege escalation, and persistence establishment. Since the md2pdf gem operates within Ruby environments, attackers could potentially leverage this vulnerability to compromise web applications that utilize the gem for document conversion services, especially in server-side contexts where user input is processed without proper validation. The vulnerability is particularly dangerous in multi-tenant environments or applications where users can upload content, as it allows for arbitrary code execution with the privileges of the application process, potentially leading to complete system compromise.
Mitigation strategies for CVE-2013-1948 should focus on immediate remediation through updating to a patched version of the md2pdf gem, as the vulnerability was addressed in subsequent releases. Organizations should implement proper input validation and sanitization measures at all levels of their applications, ensuring that any user-supplied filenames are properly escaped or filtered before being used in shell commands. The implementation of the principle of least privilege is crucial, as the conversion process should run with minimal required permissions to reduce potential impact. Additionally, organizations should consider using alternative conversion libraries that do not rely on shell command execution for processing user input, and implement proper logging and monitoring to detect suspicious command execution patterns. This vulnerability demonstrates the importance of secure coding practices and the need for thorough input validation, particularly when dealing with user-supplied data in contexts that interact with system-level operations. The ATT&CK framework would categorize this vulnerability under the T1059.001 technique for command and script interpreters, specifically shell commands, and the T1068 technique for exploit for privilege escalation, as it provides a mechanism for attackers to execute commands with elevated privileges.