Attack Surface: 1. Bytecode Interpreter Exploitation
Description: Flaws in how Hermes interprets compiled JavaScript bytecode. This is the core functionality of the engine, making it a high-priority target. How Hermes Contributes: This is the fundamental mechanism by which Hermes executes JavaScript. Any bug here directly impacts security. Example: A crafted JavaScript input that exploits a type confusion bug in the interpreter's handling of object properties, leading to out-of-bounds memory access. Impact: Arbitrary code execution within the Hermes context (severity depends on external sandboxing, but the vulnerability itself is critical within Hermes). Risk Severity: Critical Mitigation Strategies: * Developers: * Regularly update to the latest Hermes release. This is the primary mitigation for internal bugs. * Perform extensive fuzz testing of JavaScript after compilation by Hermes, focusing on edge cases and complex interactions. This helps find bugs triggered by valid JavaScript, even if the bug is in Hermes. * Implement robust error handling within the JavaScript code (this helps mitigate the impact, but doesn't fix the underlying Hermes bug). * Users: (No direct mitigation; relies entirely on developers updating Hermes)
Attack Surface: 2. JIT Compiler Vulnerabilities (if enabled)
Description: Bugs in the optional Just-In-Time (JIT) compiler, which translates bytecode to native machine code. How Hermes Contributes: The JIT compiler, if present, is a complex component of Hermes that directly handles code generation. Example: A buffer overflow in the JIT's code generation logic, triggered by a specific JavaScript pattern, allowing injection of malicious native code. Impact: Arbitrary code execution at the native level (potentially bypassing some sandboxing). Risk Severity: Critical (if JIT is enabled) Mitigation Strategies: * Developers: * Strongly consider disabling the JIT compiler if performance allows. This eliminates this entire attack surface. * If the JIT is required: * Rigorously fuzz test the JIT compiler specifically. * Keep Hermes updated. * Users: (No direct mitigation)
Attack Surface: 3. Memory Management Flaws
Description: Bugs in Hermes's internal memory management (garbage collection, allocation). How Hermes Contributes: Hermes manages its own memory; these are vulnerabilities within that system. Example: A use-after-free vulnerability in the garbage collector, triggered by a specific sequence of JavaScript object manipulations. Impact: Potential for arbitrary code execution within the Hermes context, or denial-of-service (crashes). Risk Severity: High Mitigation Strategies: * Developers: * Regularly update Hermes. This is the primary defense against internal bugs. * Fuzz testing, specifically targeting memory management, can help uncover these flaws. * Users: (No direct mitigation)
Attack Surface: 4. Built-in API Implementation Bugs
Description: Vulnerabilities in Hermes's own implementations of standard JavaScript APIs (e.g., JSON.parse, RegExp).
How Hermes Contributes: These are bugs within Hermes's code, not in how the application uses the APIs.
Example: A crafted regular expression that triggers a denial-of-service (ReDoS) vulnerability within Hermes's RegExp engine.
Impact: Denial-of-service, or potentially code execution (depending on the specific API and vulnerability).
Risk Severity: High
Mitigation Strategies:
* Developers:
* Regularly update Hermes.
* Fuzz testing focused on Hermes's implementations of the built-in APIs.
* Users: (No direct mitigation)
Attack Surface: 5. Supply Chain Compromise
Description: Malicious code introduced into the Hermes library or its dependencies. How Hermes Contributes: The application's security depends on the integrity of the Hermes library itself. Example: A compromised version of Hermes is distributed, containing a backdoor that allows arbitrary code execution. Impact: Potentially complete system compromise. Risk Severity: Critical Mitigation Strategies: * Developers: * Obtain Hermes from the official, trusted source (GitHub repository). * Verify the integrity of downloaded binaries/source code (checksums, signatures). * Use a Software Composition Analysis (SCA) tool to identify known vulnerabilities in Hermes and its dependencies. * Regularly update Hermes and all dependencies. * Users: * Use applications from trusted developers and sources. * Keep the application and its platform (OS, etc.) updated.