CVE-2018-17072 in JSON++
Summary
by MITRE
JSON++ through 2016-06-15 has a buffer over-read in yyparse() in json.y.
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Analysis
by VulDB Data Team • 05/16/2023
CVE-2018-17072 represents a critical buffer over-read vulnerability affecting JSON++ library versions up to and including the 2016-06-15 release. This vulnerability resides within the yyparse() function in the json.y file, which is part of the yacc/bison parser generator implementation used for processing json data structures. The flaw occurs when the parser encounters malformed or specially crafted json input that triggers an improper memory access pattern during the parsing process. This type of vulnerability falls under CWE-125, which specifically addresses out-of-bounds read conditions where an application attempts to read memory beyond the bounds of a valid buffer. The buffer over-read vulnerability can potentially lead to information disclosure, application crashes, or in more severe cases, remote code execution depending on the system's memory layout and the attacker's ability to control the input data. When the parser processes malformed json input, it fails to properly validate the input boundaries before accessing memory locations, causing the program to read beyond allocated buffer space. This vulnerability directly impacts the parser's ability to handle malformed input gracefully and can be exploited through input validation bypass techniques, making it particularly dangerous in applications that process untrusted json data from external sources.
The operational impact of CVE-2018-17072 extends beyond simple parsing failures as it represents a fundamental flaw in how the library handles memory access during the parsing phase. Attackers can leverage this vulnerability by crafting malicious json payloads that cause the parser to read memory locations that should not be accessible, potentially exposing sensitive data from adjacent memory regions or causing the application to crash. This vulnerability is particularly concerning in web applications, api endpoints, and any system that processes json data from untrusted sources, as it can be exploited through common attack vectors such as cross-site scripting, api injection, or data processing attacks. The attack surface is broad given that json parsing is a fundamental operation in modern applications, making this vulnerability highly exploitable in environments where json data is regularly processed. Security researchers have classified this vulnerability as high-risk due to its potential for information disclosure and system instability, with the possibility of escalation to more serious security incidents when combined with other vulnerabilities in the attack chain.
Mitigation strategies for CVE-2018-17072 should focus on immediate library updates and input validation measures to prevent exploitation. Organizations should prioritize upgrading to versions of JSON++ that contain the patched yyparse() implementation, as the maintainers have addressed the buffer over-read issue by implementing proper boundary checks and input validation. Additionally, implementing robust input sanitization and validation at the application level can provide defense-in-depth protection against exploitation attempts, particularly for applications that cannot immediately update their dependencies. Network-based mitigations such as web application firewalls and input filtering rules can help detect and block malicious json payloads that attempt to trigger the buffer over-read condition. The vulnerability also highlights the importance of proper memory management practices in parser implementations, aligning with ATT&CK technique T1059.007 for execution through scripting and T1211 for exploitation of memory corruption vulnerabilities. System administrators should monitor for potential exploitation attempts through log analysis and implement proper error handling to prevent information disclosure from memory dumps or crash information that might be exposed during exploitation attempts. Regular security assessments and penetration testing should include verification of parser library versions and their vulnerability status to ensure comprehensive protection against this and similar memory corruption vulnerabilities.