CVE-2020-23319 in JerryScript
Summary
by MITRE • 06/11/2021
There is an Assertion in '(flags >> CBC_STACK_ADJUST_SHIFT) >= CBC_STACK_ADJUST_BASE || (CBC_STACK_ADJUST_BASE - (flags >> CBC_STACK_ADJUST_SHIFT)) stack_depth' in parser_emit_cbc_backward_branch 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 parser_emit_cbc_backward_branch function where an assertion failure occurs due to improper handling of bitwise operations on stack depth calculations. The specific condition '(flags >> CBC_STACK_ADJUST_SHIFT) >= CBC_STACK_ADJUST_BASE || (CBC_STACK_ADJUST_BASE - (flags >> CBC_STACK_ADJUST_SHIFT)) stack_depth' represents a critical flaw in the JavaScript engine's bytecode compilation process. The assertion checks whether the calculated stack adjustment value exceeds a predefined base threshold or whether the difference between base and adjusted values remains within acceptable bounds. When this condition fails, it triggers an assertion that can lead to program termination or unexpected behavior during JavaScript code execution.
The technical flaw stems from improper validation of stack adjustment parameters during bytecode compilation, particularly when processing backward branch operations in the JerryScript interpreter. This vulnerability is categorized under CWE-617 as Reachable Assertion, where an assertion that should never be triggered becomes reachable due to insufficient input validation or incorrect boundary checking. The issue manifests when the bitwise right shift operation on flags variable produces values that violate the expected mathematical relationship between stack adjustment parameters and base thresholds. This type of vulnerability can be exploited to cause denial of service or potentially enable more sophisticated attacks if the assertion failure leads to memory corruption or control flow manipulation.
The operational impact of this vulnerability extends beyond simple denial of service scenarios as it affects the stability and reliability of applications that depend on JerryScript for JavaScript execution. When triggered, the assertion failure can cause the entire JavaScript engine to terminate abruptly, disrupting application functionality and potentially exposing systems to service interruption attacks. In environments where JerryScript is embedded in IoT devices, embedded systems, or mobile applications, this vulnerability could be leveraged by attackers to create persistent availability issues. The vulnerability is particularly concerning in scenarios where JavaScript code is dynamically generated or received from untrusted sources, as it may be possible to craft malicious input that specifically triggers this assertion failure.
Mitigation strategies for this vulnerability should include immediate patching to JerryScript version 2.3.0 or later where the assertion has been properly addressed through enhanced input validation and boundary checking. System administrators should implement robust input sanitization procedures for any JavaScript code that passes through the affected engine, particularly when processing external or user-generated content. The implementation of additional runtime checks and defensive programming practices can help prevent exploitation of similar bitwise operation vulnerabilities. Security monitoring should include detection of assertion failures and abnormal termination patterns in JavaScript engine processes. Organizations using JerryScript should also consider implementing application sandboxing techniques and restricting JavaScript execution privileges to minimize potential impact from exploitation attempts. This vulnerability demonstrates the importance of proper assertion design and validation in embedded JavaScript engines, aligning with ATT&CK technique T1059.007 for JavaScript and the broader category of software supply chain attacks that target core interpreter components.