CVE-2021-46489 in Jsish
Summary
by MITRE • 01/28/2022
Jsish v3.5.0 was discovered to contain a heap-use-after-free via Jsi_DecrRefCount in src/jsiValue.c. This vulnerability can lead to a Denial of Service (DoS).
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Analysis
by VulDB Data Team • 01/30/2022
The heap-use-after-free vulnerability in Jsish v3.5.0 represents a critical memory safety issue that arises from improper reference counting management within the JavaScript interpreter. This flaw exists in the Jsi_DecrRefCount function located in the src/jsiValue.c source file, where the decrementing of reference counts does not properly handle memory deallocation sequences. The vulnerability manifests when the JavaScript engine attempts to free memory that has already been released but is still being referenced, creating a dangerous state where subsequent memory operations may access invalid memory locations or corrupt heap structures.
The technical implementation of this vulnerability involves the improper management of object reference counts in the Jsish interpreter's memory management system. When Jsi_DecrRefCount processes object cleanup operations, it fails to ensure that all references to freed memory are properly invalidated before the memory is returned to the heap. This creates a window where other code paths may attempt to access the now-freed memory location, leading to unpredictable behavior and system instability. The vulnerability specifically affects the interpreter's garbage collection mechanisms and object lifecycle management, where the reference counting algorithm does not adequately prevent concurrent access to objects that are in the process of being deallocated.
The operational impact of this heap-use-after-free vulnerability extends beyond simple denial of service conditions to potentially enable more severe security consequences. While the primary effect is a denial of service that can cause the Jsish interpreter to crash or become unresponsive, the underlying memory corruption could theoretically be exploited by malicious actors to execute arbitrary code or escalate privileges within the interpreter's execution environment. Attackers could potentially craft JavaScript payloads that trigger the vulnerable code path repeatedly, leading to persistent service disruption or system compromise. The vulnerability affects any application or system utilizing Jsish v3.5.0 as its JavaScript engine, making it particularly concerning for web applications, server-side JavaScript environments, and embedded systems that rely on this interpreter.
Mitigation strategies for this vulnerability should focus on immediate patching of the Jsish interpreter to version 3.5.1 or later, which contains the necessary fixes for the reference counting implementation. Organizations should implement comprehensive monitoring of their Jsish-based applications to detect potential exploitation attempts and establish incident response procedures for handling denial of service conditions. Additionally, defensive programming measures such as implementing memory debugging tools, using address sanitizers during development, and conducting regular security code reviews should be employed to identify similar issues in other components of the software stack. The vulnerability aligns with CWE-416, which specifically addresses use-after-free errors, and could potentially map to ATT&CK techniques involving privilege escalation through memory corruption exploits. System administrators should also consider implementing application whitelisting and sandboxing measures to limit the potential impact of any exploitation attempts, while maintaining regular updates to ensure all known vulnerabilities are addressed in the interpreter's runtime environment.