CVE-2009-1697 in Safari
Summary
by MITRE
CRLF injection 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 HTTP headers and bypass the Same Origin Policy via a crafted HTML document, related to cross-site scripting (XSS) attacks that depend on communication with arbitrary web sites on the same server through use of XMLHttpRequest without a Host header.
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Analysis
by VulDB Data Team • 09/06/2019
The CVE-2009-1697 vulnerability represents a critical cross-site scripting flaw in Apple's WebKit rendering engine that affected Safari browsers and iPhone OS versions through 2.2.1. This vulnerability stems from improper handling of carriage return line feed sequences in HTTP header processing, creating a pathway for malicious actors to manipulate web communications. The flaw specifically targets the Same Origin Policy enforcement mechanism, which is fundamental to web security by preventing unauthorized access between different domains. When exploited, this vulnerability enables attackers to inject malicious HTTP headers into web requests, effectively bypassing security boundaries that should isolate web applications from each other.
The technical implementation of this CRLF injection vulnerability occurs within WebKit's HTTP header parsing routines where carriage return and line feed characters are not properly sanitized or escaped during the processing of web content. Attackers can craft malicious HTML documents that contain carefully constructed CRLF sequences which, when processed by the vulnerable WebKit engine, result in the injection of additional HTTP headers into outgoing requests. This injection occurs particularly when XMLHttpRequest objects are used to communicate with web servers without proper Host header specifications, creating a scenario where the injected headers can modify the request behavior in ways that circumvent normal security controls.
The operational impact of this vulnerability extends beyond simple cross-site scripting attacks, as it fundamentally undermines the browser's ability to enforce security boundaries between different origins. When combined with existing XSS vulnerabilities, this flaw allows attackers to manipulate the communication between web applications and servers, potentially enabling session hijacking, data theft, or privilege escalation attacks. The vulnerability is particularly dangerous because it operates at the protocol level rather than the application level, meaning that even well-designed web applications can be compromised if they rely on the browser's proper enforcement of cross-origin restrictions. This attack vector can be exploited against any web application that uses XMLHttpRequest without explicit Host header validation, making it a widespread concern across the web ecosystem.
Mitigation strategies for CVE-2009-1697 require both immediate patching and architectural considerations for web application security. The primary solution involves updating to patched versions of Safari and iPhone OS where Apple implemented proper sanitization of CRLF sequences in HTTP header processing. Organizations should also implement additional security measures such as Content Security Policy headers, proper input validation for HTTP headers, and regular security auditing of web applications to detect and prevent similar injection attacks. From a defensive perspective, this vulnerability aligns with CWE-113 which describes improper neutralization of CRLF characters in HTTP headers, and relates to ATT&CK technique T1059.001 for command and scripting interpreter usage, as attackers may leverage the injected headers to execute malicious commands or redirect traffic. The vulnerability demonstrates the importance of proper input sanitization at multiple layers of the web stack and highlights the need for comprehensive security testing that includes protocol-level validation rather than relying solely on application-level controls.