CVE-2017-11911: ChakraCore RCE Vulnerability

The analysis focuses on commit a5d6be6 which patched CVE-2017-11911. The code changes in AsmJsModule.cpp introduced a bitvector (initializerBV) to track variable usage in initializers and added validation to prevent using variables before declaration. The vulnerability occurred because the original implementation didn't ensure variables were declared before being referenced in initializers, allowing attackers to reference undefined constants and trigger OOB reads from the constant table via GetConstRegister(). The explicit error message 'Cannot declare a var after using it in an initializer' in the patch confirms this was the vulnerable path.