CVE-2020-23322 in JerryScript
Summary
by MITRE • 06/11/2021
There is an Assertion in 'context_p->token.type == LEXER_RIGHT_BRACE || context_p->token.type == LEXER_ASSIGN || context_p->token.type == LEXER_COMMA' in parser_parse_object_initializer in JerryScript 2.2.0.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 06/13/2021
The vulnerability identified as CVE-2020-23322 represents a critical assertion failure within the JerryScript JavaScript engine version 2.2.0, specifically within the parser component responsible for processing object initializers. This assertion occurs during the parsing phase when the parser encounters a specific sequence of tokens while processing JavaScript object literal syntax. The affected code segment demonstrates a logical validation check that expects certain token types but fails to properly handle all possible input scenarios, leading to potential denial of service or arbitrary code execution conditions.
The technical flaw manifests in the parser_parse_object_initializer function where the assertion evaluates three specific token types: LEXER_RIGHT_BRACE representing closing braces, LEXER_ASSIGN indicating assignment operators, and LEXER_COMMA for comma separators. When the parser encounters a token that does not match these expected types, the assertion fails and terminates the JavaScript engine process. This represents a classic example of inadequate input validation and error handling within a parsing component, which falls under CWE-248, "Uncaught Exception" and CWE-691, "Insufficient Control Flow Management". The vulnerability stems from the parser's inability to gracefully handle malformed JavaScript syntax during object initializer parsing, creating a potential attack vector for malicious actors who could craft specific JavaScript payloads to trigger this assertion failure.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it could potentially enable more sophisticated attack vectors depending on the execution environment. When the JavaScript engine crashes due to this assertion failure, it may provide attackers with opportunities to perform system-level disruptions or potentially exploit the process termination to execute code in the context of the vulnerable application. The vulnerability is particularly concerning in environments where JerryScript is embedded within web browsers or other applications that process untrusted JavaScript input, as it could be leveraged to cause service disruption or potentially escalate to more serious security implications. According to ATT&CK framework, this vulnerability aligns with T1203, "Exploitation for Client Execution" and T1499, "Endpoint Denial of Service" techniques, as it can be used to disrupt service availability through controlled assertion failures.
Mitigation strategies for CVE-2020-23322 should focus on immediate patching of the JerryScript engine to version 2.3.0 or later, where the assertion failure has been addressed through proper token validation and error handling. Organizations should also implement input sanitization measures and strict JavaScript execution policies to prevent untrusted code from reaching the parser component. Additionally, deploying runtime monitoring and anomaly detection systems can help identify potential exploitation attempts by monitoring for unusual assertion failures or process terminations. Security teams should also consider implementing sandboxing techniques and privilege separation to limit the potential impact of any successful exploitation attempts, while ensuring that all embedded JavaScript environments are regularly updated to protect against similar vulnerabilities in the future.