CVE-2012-4930 in Chrome
Summary
by MITRE
The SPDY protocol 3 and earlier, as used in Mozilla Firefox, Google Chrome, and other products, can perform TLS encryption of compressed data without properly obfuscating the length of the unencrypted data, which allows man-in-the-middle attackers to obtain plaintext HTTP headers by observing length differences during a series of guesses in which a string in an HTTP request potentially matches an unknown string in an HTTP header, aka a "CRIME" attack.
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Analysis
by VulDB Data Team • 12/30/2024
The CVE-2012-4930 vulnerability represents a critical security flaw in the SPDY protocol version 3 and earlier implementations across major web browsers including Mozilla Firefox and Google Chrome. This vulnerability stems from the protocol's improper handling of TLS encryption when compressing data, creating a fundamental weakness in the cryptographic implementation that exposes sensitive information. The issue specifically affects how compressed data is encrypted within the TLS layer, where the length of unencrypted data remains visible to attackers despite the encrypted payload. This design flaw creates a significant information disclosure risk that can be exploited through sophisticated network analysis techniques.
The technical exploitation of this vulnerability relies on the CRIME (Compression Ratio Info-leak Made Easy) attack methodology, which leverages the relationship between compressed data size and the content being compressed. When SPDY protocol compresses HTTP headers along with the encrypted data, attackers can observe subtle variations in packet lengths during network transmission. These length differences directly correlate to the size of the compressed headers, allowing malicious actors to perform statistical analysis and make educated guesses about the content of HTTP headers. The attack works by crafting specific HTTP requests and monitoring the resulting encrypted packet sizes, ultimately enabling the reconstruction of sensitive header information through iterative guessing processes.
This vulnerability has severe operational implications for web security infrastructure and user privacy protection. The attack can be executed by man-in-the-middle adversaries who can intercept and analyze network traffic without requiring advanced cryptographic breaking techniques or significant computational resources. The exposure of HTTP headers includes sensitive information such as authentication tokens, session identifiers, and other confidential data that could be used for session hijacking, credential theft, or further exploitation of web applications. The vulnerability affects not only individual user sessions but also enterprise security systems that rely on proper encryption of HTTP communications, potentially compromising entire web application architectures.
The attack vector operates through standard network interception capabilities, making it particularly dangerous as it can be executed by adversaries with minimal technical expertise. Security professionals should note that this vulnerability aligns with CWE-310, which addresses cryptographic weaknesses in data encryption implementations, and maps to ATT&CK technique T1041 for data compression and T1566 for credential access through network infiltration. Organizations should implement immediate mitigations including disabling SPDY protocol versions 3 and earlier, upgrading to SPDY version 4 or HTTP/2 implementations that properly handle compression, and deploying network monitoring solutions to detect anomalous packet length variations. Additionally, browser vendors have addressed this issue through protocol updates and security patches, but organizations must ensure comprehensive deployment across all affected systems to prevent exploitation. The vulnerability underscores the critical importance of proper cryptographic protocol design and the need for thorough security review of compression and encryption interactions in network protocols.