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attack-surface.md

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Attack Surface Analysis for facebook/hermes

Attack Surface: JIT Compiler Vulnerabilities

  • Description: Bugs within Hermes's Just-In-Time (JIT) compiler that can be exploited by malicious JavaScript code.
  • Hermes Contribution: Hermes utilizes a JIT compiler to optimize JavaScript execution, making it a potential source of vulnerabilities if not implemented securely. This is a core component of Hermes.
  • Example: A specially crafted JavaScript function triggers a buffer overflow in the JIT compiler during optimization, allowing an attacker to overwrite memory and execute arbitrary code.
  • Impact: Code Execution, Denial of Service, Information Disclosure
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Keep Hermes Up-to-Date: Regularly update Hermes to benefit from JIT compiler bug fixes and security patches.
    • Disable JIT (If Possible and Acceptable Performance Impact): In highly security-sensitive environments, consider disabling JIT compilation if performance impact is acceptable. This reduces the attack surface related to JIT bugs, but may impact application performance.

Attack Surface: Interpreter Vulnerabilities

  • Description: Bugs within Hermes's core JavaScript interpreter, even when JIT is disabled or bypassed.
  • Hermes Contribution: Hermes's interpreter is the fundamental execution engine for JavaScript, and vulnerabilities within it can be directly exploited. This is a core component of Hermes.
  • Example: A specific sequence of JavaScript operations triggers a use-after-free vulnerability in the interpreter's object management, allowing an attacker to corrupt memory and potentially gain control of execution flow.
  • Impact: Code Execution, Denial of Service, Information Disclosure
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Keep Hermes Up-to-Date: Regularly update Hermes to benefit from interpreter bug fixes and security patches.

Attack Surface: Memory Management Issues (Heap Overflow/Underflow, Use-After-Free)

  • Description: Vulnerabilities arising from incorrect memory management within Hermes, such as heap overflows, underflows, or use-after-free conditions.
  • Hermes Contribution: Hermes's memory management implementation is crucial for engine stability and security. Bugs in this area are directly within Hermes's code and can lead to exploitable vulnerabilities.
  • Example: A JavaScript operation causes Hermes to allocate insufficient memory for a data structure, leading to a heap buffer overflow when data is written beyond the allocated boundary. This can be exploited to overwrite adjacent memory regions and potentially execute code.
  • Impact: Code Execution, Denial of Service, Information Disclosure
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Keep Hermes Up-to-Date: Regularly update Hermes to benefit from memory management bug fixes and security patches.

Attack Surface: Bytecode Verification Bypass

  • Description: Vulnerabilities in the process of verifying Hermes bytecode, allowing malicious or invalid bytecode to be executed.
  • Hermes Contribution: Hermes compiles JavaScript to bytecode for faster startup. The bytecode verification is a Hermes specific security feature, and vulnerabilities here are directly within Hermes.
  • Example: A crafted bytecode file exploits a flaw in the bytecode verification logic, allowing it to pass verification despite containing malicious instructions that would normally be rejected. This malicious bytecode then executes within the Hermes engine.
  • Impact: Code Execution, Denial of Service
  • Risk Severity: High
  • Mitigation Strategies:
    • Keep Hermes Up-to-Date: Regularly update Hermes to benefit from bytecode verification bug fixes and security patches.
    • Secure Bytecode Distribution: Ensure bytecode is distributed securely and is not tampered with after compilation. Use integrity checks (e.g., checksums) to verify bytecode integrity before loading.

Attack Surface: Bytecode Deserialization Bugs

  • Description: Vulnerabilities in the process of deserializing Hermes bytecode from storage or network into memory.
  • Hermes Contribution: Hermes needs to deserialize bytecode for execution. Bugs in this deserialization process are directly within Hermes's bytecode handling code and can be exploited with malicious bytecode.
  • Example: A specially crafted bytecode file exploits a buffer overflow vulnerability during deserialization, allowing an attacker to overwrite memory and potentially execute code before the bytecode is even executed as JavaScript.
  • Impact: Code Execution, Denial of Service
  • Risk Severity: High
  • Mitigation Strategies:
    • Keep Hermes Up-to-Date: Regularly update Hermes to benefit from bytecode deserialization bug fixes and security patches.

Attack Surface: Remote Debugging Protocol Vulnerabilities (If Enabled in Production)

  • Description: Vulnerabilities in the remote debugging protocol used to inspect and control Hermes execution, if inadvertently left enabled in production builds.
  • Hermes Contribution: Hermes may offer remote debugging capabilities for development. The debugging protocol and its vulnerabilities are directly related to Hermes's features.
  • Example: A vulnerability in the debugging protocol allows an unauthenticated attacker to connect to a production application's Hermes instance and inject arbitrary JavaScript code through the debugging interface.
  • Impact: Code Execution, Information Disclosure, Control Flow Manipulation
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Disable Remote Debugging in Production: Absolutely ensure remote debugging features are completely disabled in production builds. This is the most critical mitigation.