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Attack Surface Analysis for mozilla/pdf.js

Attack Surface: Memory Corruption (Parsing Engine)

  • Description: Vulnerabilities in the PDF parsing engine that lead to memory corruption, such as buffer overflows, use-after-free errors, or type confusion. These are often the most dangerous class of vulnerabilities.
  • How pdf.js Contributes: pdf.js's core function is parsing complex, potentially malformed PDF files. The parsing process involves handling numerous data structures and algorithms, increasing the likelihood of memory-related errors.
  • Example: A crafted PDF with a specially designed image stream that triggers a buffer overflow in the image decoding component of pdf.js, allowing the attacker to overwrite adjacent memory.
  • Impact: Arbitrary code execution within the context of the pdf.js worker (which runs in the user's browser). This could lead to data theft, further exploitation of the browser, or installation of malware.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Developer:
      • Keep pdf.js updated to the latest version. This is the most crucial mitigation.
      • Advocate for/contribute to memory safety improvements in the pdf.js codebase (upstream).
    • User:
      • Only open PDFs from trusted sources.
      • Keep your browser and any PDF reader plugins updated.

Attack Surface: Unintended JavaScript Execution

  • Description: Exploitation of vulnerabilities in pdf.js's JavaScript handling mechanisms to execute arbitrary JavaScript code, even when JavaScript is supposedly sandboxed or restricted.
  • How pdf.js Contributes: pdf.js includes a JavaScript engine to support interactive PDF features. While it attempts to sandbox this engine, vulnerabilities in the sandboxing or in the handling of JavaScript events can lead to bypasses.
  • Example: A PDF contains a malicious JavaScript action that exploits a flaw in the pdf.js sandbox, allowing it to access the DOM of the parent page or make cross-origin requests.
  • Impact: Cross-site scripting (XSS) within the context of the application, potentially leading to data theft, session hijacking, or defacement. The impact is limited by the browser's same-origin policy, but the pdf.js worker context might offer some bypass opportunities.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developer:
      • Disable JavaScript execution in pdf.js if interactive features are not needed. This is a configuration option.
      • Keep pdf.js updated.
    • User:
      • Be cautious about opening PDFs with interactive elements from untrusted sources.

Attack Surface: Dependency Vulnerabilities

  • Description: Vulnerabilities in libraries that pdf.js depends on (e.g., image decoding libraries) can be exploited through pdf.js.
  • How pdf.js Contributes: pdf.js relies on external libraries for certain functionalities. If these libraries have vulnerabilities, they can be triggered when pdf.js processes specific PDF content.
  • Example: A vulnerability exists in a JPEG2000 decoding library used by pdf.js. A crafted PDF containing a malicious JPEG2000 image exploits this vulnerability, leading to code execution.
  • Impact: Similar to direct pdf.js vulnerabilities, this can lead to arbitrary code execution, data theft, or denial of service.
  • Risk Severity: High to Critical (depending on the dependency vulnerability)
  • Mitigation Strategies:
    • Developer:
      • Monitor security advisories related to pdf.js and its dependencies.
      • Keep pdf.js updated, as updates often include updates to bundled dependencies.
    • User: Keep your browser and any PDF reader plugins updated.