CVE-2014-4994 in gyazo Gem
Summary
by MITRE
lib/gyazo/client.rb in the gyazo gem 1.0.0 for Ruby allows local users to write to arbitrary files via a symlink attack on a temporary file, related to time-based filenames.
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Analysis
by VulDB Data Team • 12/21/2019
The vulnerability identified as CVE-2014-4994 resides within the gyazo gem version 1.0.0 for Ruby, specifically in the lib/gyazo/client.rb file where a critical security flaw enables local privilege escalation through improper temporary file handling. This issue manifests as a symlink attack vulnerability that exploits the gem's use of time-based filenames for temporary file creation, creating a window of opportunity for malicious actors to manipulate the system's file operations.
The technical flaw stems from the gem's insecure handling of temporary files during screenshot capture operations, where it creates temporary files using predictable time-based naming conventions without proper security checks. When a local user can influence the creation of these temporary files through symbolic link manipulation, they can redirect file writes to arbitrary locations on the filesystem. This represents a classic race condition vulnerability where the timing between file creation and access allows for exploitation.
The operational impact of this vulnerability extends beyond simple file manipulation, as it enables attackers to potentially overwrite critical system files, inject malicious content into applications, or escalate privileges within the affected system. The vulnerability is particularly concerning because it operates at the local user level, meaning that any user with access to the system can exploit this weakness to gain unauthorized access to write operations in directories where the gem is executed. This type of vulnerability aligns with CWE-367, which describes the Time-of-Check to Time-of-Use (TOCTOU) race condition, and demonstrates how improper file handling can lead to privilege escalation.
Mitigation strategies for this vulnerability must address the fundamental flaw in temporary file creation practices within the gyazo gem. The recommended approach involves implementing proper temporary file handling techniques that avoid predictable naming schemes and ensure atomic file creation operations. System administrators should immediately update to patched versions of the gyazo gem where available, and organizations should conduct comprehensive audits of their Ruby applications to identify any other instances of similar vulnerable patterns. Security controls should include monitoring for unauthorized file system modifications and implementing proper file permissions to limit write access to temporary directories. The vulnerability also highlights the importance of following secure coding practices as outlined in the OWASP Secure Coding Practices and aligns with ATT&CK technique T1059.007 for execution through scripting, where local privilege escalation can enable further attack vectors within compromised systems.