CVE-2009-1691 in Safari
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in WebKit in Apple Safari before 4.0, iPhone OS 1.0 through 2.2.1, and iPhone OS for iPod touch 1.1 through 2.2.1 allows remote attackers to inject arbitrary web script or HTML via vectors related to insufficient access control for standard JavaScript prototypes in other domains.
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Analysis
by VulDB Data Team • 09/06/2019
The vulnerability described in CVE-2009-1691 represents a critical cross-site scripting flaw within the WebKit rendering engine that powered Apple Safari browsers and iPhone OS web views. This issue affected a broad range of Apple products including Safari versions prior to 4.0 and various iterations of iPhone OS from 1.0 through 2.2.1 for both iPhone and iPod touch devices. The flaw emerged from inadequate access control mechanisms that governed JavaScript prototype objects across different domains, creating a pathway for malicious actors to execute unauthorized code within web contexts. The vulnerability specifically exploited the permissive nature of prototype inheritance in JavaScript, allowing attackers to manipulate standard JavaScript objects that should have been restricted to their originating domains.
The technical exploitation of this vulnerability leveraged the fundamental architecture of JavaScript's prototype chain mechanism, which was designed to enable code reuse and inheritance patterns. Under normal circumstances, JavaScript prototypes should maintain strict domain isolation to prevent cross-domain script injection attacks. However, the flaw in WebKit's implementation allowed attackers to bypass these security boundaries by accessing and modifying prototype objects from other domains. This created a scenario where malicious scripts could be injected into web pages through seemingly benign input vectors, potentially leading to unauthorized access to user data, session hijacking, or complete browser compromise. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and demonstrates how improper access control can create persistent security weaknesses in browser implementations.
The operational impact of this vulnerability was substantial across Apple's ecosystem, affecting millions of users who relied on Safari browsers and iPhone web applications. Attackers could craft malicious websites that would execute arbitrary JavaScript code when users visited them, potentially stealing cookies, session tokens, or other sensitive information. The attack surface was particularly concerning given the widespread use of Safari and iPhone OS devices, with the vulnerability potentially enabling man-in-the-middle attacks where users could be redirected to malicious sites that exploited this flaw. Users browsing the web on affected devices were at risk of having their personal information compromised, and organizations using Safari-based applications faced potential security breaches that could impact their web applications and user data. The vulnerability also aligned with ATT&CK technique T1566, which covers spearphishing attacks that leverage web-based exploits to gain initial access to target systems.
Mitigation strategies for this vulnerability required immediate action from Apple to release security updates that would patch the prototype access control mechanisms within WebKit. Users were advised to upgrade to Safari 4.0 or later versions and to update their iPhone OS to versions that contained the necessary security patches. Organizations needed to implement additional network-level protections and web application firewalls to detect and prevent exploitation attempts. The fix involved strengthening the security boundaries around JavaScript prototype objects to ensure proper domain isolation, preventing unauthorized access to prototype methods and properties across different web origins. This vulnerability highlighted the critical importance of proper access control implementations in browser engines and the potential for seemingly minor security flaws to create widespread exploitation opportunities across multiple platforms and device types.