CVE-2017-0898 in macOS
Summary
by MITRE
Ruby before 2.4.2, 2.3.5, and 2.2.8 is vulnerable to a malicious format string which contains a precious specifier (*) with a huge minus value. Such situation can lead to a buffer overrun, resulting in a heap memory corruption or an information disclosure from the heap.
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Analysis
by VulDB Data Team • 05/10/2026
The vulnerability identified as CVE-2017-0898 represents a critical format string vulnerability affecting multiple versions of the Ruby programming language including versions prior to 2.4.2, 2.3.5, and 2.2.8. This flaw resides in Ruby's handling of format strings within its string formatting functions, specifically when processing the precision specifier asterisk (*) in combination with extremely large negative values. The vulnerability stems from insufficient input validation and bounds checking in the format string processing logic, creating a pathway for malicious actors to manipulate memory layout through carefully crafted format specifiers.
The technical exploitation of this vulnerability occurs when Ruby processes a format string containing the precision specifier (*) followed by a very large negative number. This specific combination triggers improper memory management within the Ruby interpreter's string formatting routines, leading to a buffer overrun condition. The heap memory corruption resulting from this flaw can manifest in various ways including arbitrary code execution, denial of service, or information disclosure from heap memory regions. The vulnerability is particularly dangerous because it allows attackers to manipulate memory addresses and potentially extract sensitive data from the heap, making it a significant concern for applications processing untrusted input through Ruby's formatting functions.
From an operational impact perspective, this vulnerability affects any Ruby application that processes user-supplied format strings or handles external input through string formatting operations. The risk is amplified in web applications, APIs, and any system where user input is directly processed through Ruby's printf-style formatting functions. The vulnerability can be exploited through various attack vectors including web applications, command-line tools, or any Ruby process that accepts format strings from external sources. Organizations running affected Ruby versions face potential data breaches, system compromise, and service disruption depending on how extensively format string operations are used within their applications.
Security professionals should implement immediate mitigations by upgrading to Ruby versions 2.4.2, 2.3.5, or 2.2.8, which contain patches addressing the format string vulnerability. Additionally, applications should avoid processing untrusted input through Ruby's string formatting functions where possible, and implement proper input validation and sanitization measures. The vulnerability aligns with CWE-134 which describes format string vulnerabilities, and can be mapped to ATT&CK technique T1059.007 for script-based execution and T1068 for privilege escalation through memory corruption attacks. Organizations should also monitor for potential exploitation attempts through network traffic analysis and application logs, particularly looking for unusual string formatting patterns or memory access anomalies that might indicate exploitation attempts.