CVE-2009-1600 in Safari
Summary
by MITRE
Apple Safari executes DOM calls in response to a javascript: URI in the target attribute of a submit element within a form contained in an inline PDF file, which might allow remote attackers to bypass intended Adobe Acrobat JavaScript restrictions on accessing the document object, as demonstrated by a web site that permits PDF uploads by untrusted users, and therefore has a shared document.domain between the web site and this javascript: URI. NOTE: the researcher reports that Adobe s position is "a PDF file is active content."
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Analysis
by VulDB Data Team • 12/08/2017
This vulnerability represents a sophisticated cross-domain scripting issue that exploits the interaction between Apple Safari's handling of javascript: URIs and Adobe Acrobat's JavaScript restrictions within inline PDF content. The flaw occurs when a malicious PDF file contains a form element with a submit button that references a javascript: URI in its target attribute, creating a scenario where DOM operations execute outside the intended security boundaries established by Adobe's JavaScript sandbox. The vulnerability specifically targets the document.domain property which serves as a critical security mechanism for cross-origin resource sharing and access control. When a PDF file is embedded inline within a web page and contains such malicious form elements, the browser's JavaScript execution context can inadvertently grant access to the parent document's object model, bypassing Adobe's intended security restrictions.
The technical exploitation involves a complex interplay between browser security models and PDF rendering engines, where the javascript: URI in the target attribute of a submit element triggers DOM calls that operate in a context where the PDF's document.domain has been shared with the hosting web page. This sharing occurs through the PDF's embedded JavaScript engine, which can manipulate the document.domain property to align with the parent page's domain, thereby breaking the security isolation that Adobe Acrobat typically enforces. The vulnerability is particularly dangerous because it leverages the trust relationship between the PDF viewer and the web page, allowing attackers to execute arbitrary JavaScript code with the privileges of the hosting domain. This represents a classic case of privilege escalation through improper security boundary enforcement, where the PDF rendering engine fails to maintain the expected security context that should prevent access to the parent document's JavaScript objects.
The operational impact of this vulnerability extends beyond simple cross-site scripting attacks, as it enables attackers to potentially access sensitive data, manipulate the user interface, or perform actions that would normally be restricted by Adobe's JavaScript security model. When combined with a web site that permits PDF uploads from untrusted users, this vulnerability creates a persistent attack vector where malicious PDF files can be uploaded and then executed in the context of legitimate web pages. The attacker can leverage this to steal cookies, perform unauthorized actions, or redirect users to malicious content. This vulnerability particularly affects web applications that rely on PDF processing and user-uploaded content, as it allows attackers to bypass the security controls that should prevent PDF files from accessing the parent document's JavaScript environment. The attack requires no user interaction beyond viewing the malicious PDF, making it particularly insidious and difficult to detect through traditional security monitoring approaches.
Mitigation strategies should focus on implementing strict content security policies that prevent the execution of javascript: URIs within PDF contexts, and enforcing proper document.domain isolation between PDF content and web pages. Organizations should consider disabling inline PDF rendering in web browsers where possible, or implementing additional security controls such as sandboxing mechanisms that prevent PDF content from accessing the parent document's JavaScript objects. Browser vendors should ensure that their PDF rendering engines properly enforce security boundaries and do not allow cross-domain access through javascript: URI execution. The vulnerability highlights the importance of maintaining clear security boundaries between different content types within web browsers, and represents a specific case where the ATT&CK framework would categorize this under privilege escalation techniques through improper security boundary enforcement. This type of vulnerability is particularly relevant to CWE-79, which addresses cross-site scripting flaws, and CWE-94, which covers improper control of generation of code, as it involves the execution of untrusted code in a context where security restrictions have been bypassed.