CVE-2023-48183 in QuickJS
Summary
by MITRE • 04/23/2024
QuickJS before c4cdd61 has a build_for_in_iterator NULL pointer dereference because of an erroneous lexical scope of "this" with eval.
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Analysis
by VulDB Data Team • 10/15/2025
The vulnerability identified as CVE-2023-48183 affects the QuickJS JavaScript engine version prior to commit c4cdd61 and represents a critical NULL pointer dereference flaw that emerges during the execution of build_for_in_iterator operations. This issue specifically manifests when the engine encounters erroneous lexical scoping of the "this" keyword within eval contexts, creating a scenario where memory access violations can occur. The vulnerability resides in the interpreter's handling of dynamic code execution and scope resolution mechanisms, particularly when processing for-in loop iterations that involve evaluated code fragments.
The technical root cause of this vulnerability stems from improper handling of the lexical scope binding for the "this" keyword when eval is invoked within specific code contexts. During the build_for_in_iterator process, the QuickJS engine attempts to resolve the "this" binding within the scope chain, but due to flawed implementation logic, it may attempt to dereference a NULL pointer when accessing scope-related metadata. This occurs because the engine's scope resolution algorithm fails to properly account for the dynamic nature of eval execution contexts, leading to memory corruption when the interpreter tries to access uninitialized or improperly resolved scope objects. The flaw demonstrates characteristics consistent with CWE-476 Null Pointer Dereference, where a pointer expected to contain a valid memory address instead points to NULL, causing program termination or potential code execution.
The operational impact of this vulnerability extends beyond simple program crashes, as it can potentially enable remote code execution in scenarios where malicious JavaScript code is processed by applications using the vulnerable QuickJS engine. Attackers could craft specifically designed input that triggers the NULL pointer dereference during eval operations within for-in loops, potentially leading to arbitrary code execution on systems running vulnerable software. This risk is particularly concerning given QuickJS's use in embedded systems, web browsers, and server-side applications where JavaScript execution is common. The vulnerability affects the engine's stability and security posture, making it a significant concern for developers and system administrators who rely on QuickJS for JavaScript processing capabilities. The flaw's exploitation potential aligns with ATT&CK technique T1059.007 for Scripting and T1203 for Exploitation for Client Execution, as it can be leveraged to execute malicious code through JavaScript injection vectors.
Mitigation strategies for CVE-2023-48183 require immediate application of the patch available in commit c4cdd61 or subsequent versions that address the lexical scope resolution issue within eval contexts. System administrators should prioritize updating all affected QuickJS installations and conduct thorough security assessments of applications that utilize this JavaScript engine. Organizations should implement runtime monitoring to detect anomalous JavaScript execution patterns that might indicate exploitation attempts, particularly focusing on eval operations within loop constructs. Additionally, developers should review their code for improper use of eval statements and consider alternative approaches to dynamic code execution that do not expose the engine to this specific vulnerability. The fix addresses the core issue by ensuring proper scope chain resolution and null pointer validation during build_for_in_iterator operations, preventing the erroneous access that previously led to system instability and potential remote code execution scenarios.