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Threat Model Analysis for naptha/tesseract.js

Threat: Malicious Image Upload (Client-Side Exploitation - High Severity Scenario)

Description: An attacker uploads a specifically crafted image file meticulously designed to exploit a critical vulnerability within tesseract.js's image processing or the underlying Tesseract engine. This goes beyond simple DoS and targets exploitable bugs like buffer overflows, memory corruption, or logic flaws in the core OCR processing. The attacker aims to leverage these vulnerabilities to achieve more severe impacts than just client-side DoS.

Impact: Potentially Browser Crashes due to memory corruption, Unexpected Application Behavior leading to security bypasses, or in extreme scenarios, theoretical possibilities of limited code execution within the browser's JavaScript environment if combined with other browser vulnerabilities (though less likely in typical browser sandbox).

Affected Component: tesseract.js image processing module, underlying Tesseract engine (compiled to JavaScript/WASM).

Risk Severity: High

Mitigation Strategies:

  • Rigorous client-side input validation: Implement robust checks on image file headers, formats, and potentially even content structure before processing with tesseract.js.
  • Server-side image validation and sanitization: Perform image validation and potentially pre-processing on the server before sending images to the client for OCR. This adds a layer of defense.
  • Maintain up-to-date tesseract.js version: Immediately apply security patches and updates for tesseract.js to address known vulnerabilities.
  • Implement robust error handling and security monitoring: Detect and log unusual image processing errors that might indicate exploitation attempts.

Threat: Known Vulnerabilities in tesseract.js or Tesseract Engine

Description: tesseract.js or the underlying Tesseract OCR engine (even when compiled to JavaScript/WASM) may contain publicly disclosed or zero-day vulnerabilities. Attackers actively seek and exploit these vulnerabilities in widely used libraries. If an application uses a vulnerable version of tesseract.js, it becomes susceptible to attacks targeting these known weaknesses. Exploitation methods are specific to each vulnerability.

Impact: Remote Code Execution (while less common in browser JavaScript, vulnerabilities could theoretically be chained with browser weaknesses), Data Exposure (leakage of sensitive data processed by OCR), Denial of Service (application crashes, resource exhaustion leading to server or client-side unavailability).

Affected Component: Core tesseract.js library, underlying Tesseract engine code.

Risk Severity: Critical

Mitigation Strategies:

  • Proactive Security Monitoring: Continuously monitor security advisories, vulnerability databases (like CVE, NVD), and tesseract.js release notes for reported vulnerabilities.
  • Immediate Patching and Updates: Establish a process for promptly applying security patches and updating tesseract.js to the latest stable version as soon as vulnerabilities are disclosed and fixes are available.
  • Software Composition Analysis (SCA): Utilize SCA tools to automatically scan your project's dependencies, including tesseract.js, for known vulnerabilities and alert you to necessary updates.
  • Security Audits and Penetration Testing: Conduct regular security audits and penetration testing of applications using tesseract.js to proactively identify and address potential vulnerabilities before they can be exploited.

Threat: Cross-Site Scripting (XSS) via Maliciously Crafted OCR Output

Description: While less likely from typical OCR output, in specific scenarios, or due to bugs in tesseract.js's text extraction, the text produced by tesseract.js could inadvertently contain or be manipulated to include malicious HTML or JavaScript code. If the application naively displays this OCR output without rigorous sanitization, an attacker can inject and execute arbitrary scripts in the user's browser. This could be achieved by crafting images with text designed to produce specific malicious output after OCR.

Impact: Cross-Site Scripting (XSS) - Attackers can execute arbitrary JavaScript code within the user's browser session. This allows for a wide range of malicious actions, including session hijacking, cookie theft, data exfiltration, website defacement, redirection to malicious sites, and more.

Affected Component: tesseract.js output (text result), application's output rendering and handling logic.

Risk Severity: High

Mitigation Strategies:

  • Mandatory and Robust Output Encoding/Sanitization: Always and without exception, sanitize and encode the text output from tesseract.js before displaying it in any part of the application. Use context-aware output encoding (e.g., HTML escaping for HTML contexts, JavaScript escaping for JavaScript contexts).
  • Content Security Policy (CSP) Implementation: Implement a strong Content Security Policy (CSP) to significantly reduce the impact of XSS vulnerabilities, even if they bypass sanitization in some cases. CSP can restrict the sources from which scripts can be loaded and other browser behaviors to limit the damage from XSS.
  • Regular Security Review of Output Handling: Periodically review the application's code that handles and displays tesseract.js output to ensure proper sanitization is consistently applied and that no bypasses are introduced during development.