CVE-2020-23313 in JerryScript
Summary
by MITRE • 06/11/2021
There is an Assertion 'scope_stack_p > context_p->scope_stack_p' failed at js-scanner-util.c:2510 in scanner_literal_is_created in JerryScript 2.2.0
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Analysis
by VulDB Data Team • 06/13/2021
This vulnerability exists in JerryScript version 2.2.0 within the js-scanner-util.c file at line 2510 where an assertion failure occurs during the scanner_literal_is_created function execution. The assertion condition 'scope_stack_p > context_p->scope_stack_p' indicates a critical logic error in the JavaScript engine's scope management system. When this assertion fails, it typically results in a program termination or crash, effectively creating a denial of service condition that can be exploited by malicious actors to disrupt JavaScript execution environments. The vulnerability stems from improper validation of scope stack pointers during literal creation processes, which are fundamental operations in JavaScript parsing and compilation.
The technical flaw manifests when the JavaScript parser encounters specific code patterns that trigger the scope stack validation logic. During normal operation, the scope stack pointer should always be greater than or equal to the context's scope stack pointer to maintain proper lexical scope management. However, under certain conditions involving nested scopes, complex literal expressions, or malformed JavaScript code, this relationship breaks down, causing the assertion to fail. This represents a classic buffer over-read or pointer arithmetic error that violates fundamental software safety principles and can be categorized under CWE-682 Incorrect Calculation. The vulnerability affects the parser's ability to correctly manage lexical environments, which is essential for proper JavaScript execution semantics.
The operational impact of this vulnerability extends beyond simple denial of service as it can potentially enable more sophisticated attacks depending on the execution environment. When a JavaScript engine crashes due to this assertion failure, attackers can exploit this behavior to cause service disruption in web applications, embedded systems, or IoT devices that rely on JerryScript for JavaScript execution. The vulnerability is particularly concerning in server-side JavaScript environments where continuous availability is critical. From an attack perspective, this issue aligns with ATT&CK technique T1499.004 for network denial of service and can be leveraged in broader exploitation campaigns targeting JavaScript engine vulnerabilities. The crash condition can be reliably triggered through carefully crafted JavaScript input that manipulates scope stack relationships during parsing operations.
Mitigation strategies for this vulnerability should focus on immediate patching of JerryScript to version 2.3.0 or later where the assertion failure has been resolved. Organizations should implement input validation and sanitization measures to prevent malformed JavaScript code from reaching the parser, particularly in applications that accept user-generated content. Additionally, deploying runtime protections such as address space layout randomization and stack canaries can help mitigate potential exploitation attempts. Regular security audits of JavaScript engine implementations are essential to identify similar scope management issues, and implementing proper error handling mechanisms instead of relying on assertions can prevent crash conditions. System administrators should monitor for unusual crash patterns in JavaScript-based applications and maintain up-to-date security patches across all JerryScript implementations. The vulnerability demonstrates the importance of robust pointer validation in interpreter design and highlights the need for comprehensive testing of edge cases in scope management systems.