CVE-2007-3121 in Zapping VBI Library
Summary
by MITRE
Buffer overflow in the CCdecode function in contrib/ntsc-cc.c in the zvbi-ntsc-cc tool in Zapping VBI Library (ZVBI) before 0.2.25 allows attackers to cause a denial of service (application crash) and possibly execute arbitrary code via long data during a reception error. NOTE: some of these details are obtained from third party information.
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Analysis
by VulDB Data Team • 08/19/2017
The vulnerability identified as CVE-2007-3121 represents a critical buffer overflow flaw within the Zapping VBI Library's zvbi-ntsc-cc tool, specifically affecting versions prior to 0.2.25. This issue resides in the CCdecode function located in the contrib/ntsc-cc.c source file, which processes closed caption data during television signal reception. The vulnerability manifests when the tool encounters reception errors and processes long data sequences, creating a scenario where attacker-controlled input can exceed the allocated buffer boundaries and overwrite adjacent memory regions. This type of flaw falls under CWE-121, which categorizes buffer overflow conditions where insufficient bounds checking allows memory corruption during data processing operations.
The technical implementation of this vulnerability exploits the lack of proper input validation within the CCdecode function, which handles NTSC closed caption data processing for television signal decoding. When the tool receives malformed or excessively long data packets during reception error conditions, the function fails to properly validate the data length before copying it into fixed-size buffers. This allows attackers to craft malicious input sequences that exceed buffer capacity, leading to stack corruption and potential code execution. The operational impact is significant as this vulnerability can be triggered during normal operation when the tool processes television signals, particularly during reception errors when the system attempts to decode closed caption data. The attack vector is particularly concerning because it requires no special privileges beyond normal tool execution, making it accessible to unauthenticated attackers who can cause system instability through carefully crafted input data.
The consequences of exploitation extend beyond simple denial of service to potentially enable arbitrary code execution, making this a severe security vulnerability that can compromise system integrity. When the buffer overflow occurs, it can overwrite return addresses, function pointers, or other critical memory structures, allowing attackers to redirect program execution flow and potentially inject malicious code. This vulnerability aligns with ATT&CK technique T1203, which describes exploitation of software vulnerabilities to gain system access, and specifically targets the execution phase of the attack lifecycle. The vulnerability's impact is particularly concerning in broadcast processing environments where ZVBI tools are used for television signal decoding and closed caption processing, as these systems may be exposed to untrusted input from broadcast sources or malicious actors attempting to disrupt service or gain unauthorized access to systems processing television data.
Mitigation strategies for CVE-2007-3121 require immediate patching of affected ZVBI installations to version 0.2.25 or later, which includes proper bounds checking and input validation within the CCdecode function. Organizations should implement input sanitization measures that validate data length and content before processing, particularly for any system components that handle television signal data or closed caption information. Network segmentation and access controls should be implemented to limit exposure of affected systems to untrusted broadcast data sources. Additionally, system monitoring should be enhanced to detect unusual processing patterns or crashes that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management practices and input validation in multimedia processing applications, particularly those handling real-time data streams from potentially untrusted sources. Security teams should also conduct thorough vulnerability assessments of other legacy multimedia processing tools that may contain similar buffer overflow flaws, as this represents a common class of vulnerability in signal processing and multimedia applications that handle external data inputs.