CVE-2017-14749 in JerryScript
Summary
by MITRE
JerryScript 1.0 allows remote attackers to cause a denial of service (jmem_heap_alloc_block_internal heap memory corruption) or possibly execute arbitrary code via a crafted .js file, because unrecognized \ characters cause incorrect 0x00 characters in bytecode.literal data.
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Analysis
by VulDB Data Team • 12/30/2022
CVE-2017-14749 represents a critical vulnerability in JerryScript version 1.0 that demonstrates a fundamental flaw in JavaScript engine memory management and input validation. This vulnerability resides within the jmem_heap_alloc_block_internal function where improper handling of unrecognized escape sequences leads to heap memory corruption. The flaw specifically manifests when the JavaScript engine encounters crafted \ characters within .js files that result in incorrect null byte insertion within bytecode.literal data structures. This issue falls under the CWE-121 heap-based buffer overflow category, where the improper allocation and management of heap memory creates conditions for both denial of service and potential code execution. The vulnerability operates at the intersection of memory corruption and code injection attacks, making it particularly dangerous in environments where untrusted JavaScript code is executed.
The technical exploitation of this vulnerability occurs through the manipulation of escape sequences within JavaScript source code that the engine fails to properly parse or validate. When JerryScript processes a maliciously crafted .js file containing unrecognized \ characters, the parser incorrectly converts these sequences into null bytes within the literal data section of the bytecode. This corruption of the literal data structure directly impacts the heap memory allocation process, causing jmem_heap_alloc_block_internal to attempt allocating memory blocks with corrupted metadata. The resulting heap corruption can manifest as either a denial of service condition where the engine crashes due to invalid memory access or, in more sophisticated exploitation scenarios, arbitrary code execution through memory corruption that allows attackers to overwrite critical program structures or function pointers.
The operational impact of CVE-2017-14749 extends beyond simple service disruption to encompass potential system compromise in environments where JerryScript is used as a JavaScript engine. This vulnerability affects systems that rely on JerryScript for embedded scripting capabilities, web applications, or IoT devices that utilize this engine for JavaScript execution. The attack surface is particularly broad given JerryScript's use in various embedded systems and web frameworks. From an ATT&CK perspective, this vulnerability maps to T1059.007 (Scripting) and T1068 (Exploitation for Privilege Escalation) where attackers can leverage the scripting capabilities to execute malicious payloads through corrupted heap memory. The vulnerability's severity is amplified by its potential for remote code execution, which aligns with the ATT&CK technique T1203 (Exploitation for Client Execution) where attackers can deliver malicious JavaScript payloads to vulnerable systems.
Mitigation strategies for CVE-2017-14749 require immediate patching of JerryScript to version 2.0 or later where the vulnerability has been addressed through improved input validation and escape sequence handling. Organizations should implement strict input validation for all JavaScript code execution, particularly in environments where untrusted code is processed. The fix involves enhancing the parser to properly validate escape sequences and prevent the insertion of null bytes into literal data structures during bytecode generation. Security measures should include runtime monitoring for unusual memory allocation patterns and heap corruption indicators. Additionally, organizations should consider implementing sandboxing techniques and input sanitization to reduce the impact of similar vulnerabilities. The vulnerability underscores the importance of proper memory management in scripting engines and highlights the need for comprehensive testing of escape sequence handling in JavaScript parsers. This issue serves as a reminder of the critical nature of input validation in interpreted languages and the potential for seemingly benign parsing errors to result in severe security implications.