CVE-2018-8780 in macOS
Summary
by MITRE
In Ruby before 2.2.10, 2.3.x before 2.3.7, 2.4.x before 2.4.4, 2.5.x before 2.5.1, and 2.6.0-preview1, the Dir.open, Dir.new, Dir.entries and Dir.empty? methods do not check NULL characters. When using the corresponding method, unintentional directory traversal may be performed.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 05/10/2026
The vulnerability described in CVE-2018-8780 represents a critical directory traversal flaw affecting multiple versions of the Ruby programming language. This issue stems from insufficient input validation within core directory manipulation methods, specifically Dir.open, Dir.new, Dir.entries, and Dir.empty?. The flaw allows attackers to exploit NULL character handling to bypass intended directory access restrictions and potentially gain unauthorized access to system resources. Such vulnerabilities are particularly dangerous in web applications where user input is often processed through directory operations, creating potential pathways for attackers to explore arbitrary filesystem locations beyond the intended scope.
The technical root cause of this vulnerability aligns with CWE-22, which identifies improper limitation of a pathname to a restricted directory, commonly known as directory traversal or path traversal attacks. When Ruby processes directory operations without properly validating input for NULL characters, it fails to sanitize user-supplied paths before performing filesystem operations. This weakness enables attackers to construct malicious input strings containing NULL characters that can manipulate the directory traversal behavior, effectively allowing access to directories outside the intended application scope. The vulnerability affects Ruby versions across multiple release lines, including 2.2.10, 2.3.7, 2.4.4, 2.5.1, and 2.6.0-preview1, indicating a widespread impact across the Ruby ecosystem.
From an operational standpoint, this vulnerability presents significant security risks to Ruby applications that handle user input through directory operations. Attackers could leverage this flaw to perform unauthorized file system access, potentially leading to information disclosure, data exfiltration, or even system compromise. The impact extends beyond simple directory enumeration, as successful exploitation could allow attackers to access sensitive configuration files, application data, or system resources that should remain protected. This vulnerability particularly affects web applications where user input might be passed directly to directory methods without proper sanitization, creating a direct attack surface for malicious actors.
Organizations should immediately implement mitigations by upgrading to patched Ruby versions that address this directory traversal vulnerability. The remediation strategy should include comprehensive input validation for all directory-related operations, implementing proper path sanitization techniques, and ensuring that user-supplied input undergoes thorough validation before being processed by directory methods. Additionally, system administrators should review application code to identify and remediate any instances where user input is directly passed to Dir.open, Dir.new, Dir.entries, or Dir.empty? methods. Security teams should also consider implementing network-level protections such as web application firewalls and monitoring for suspicious directory traversal patterns. The ATT&CK framework categorizes this type of vulnerability under T1083 - File and Directory Discovery, emphasizing the reconnaissance phase that attackers often use to map system resources before executing more destructive attacks. Regular security assessments and code reviews focusing on input validation practices are essential to prevent similar vulnerabilities from emerging in future application development cycles.