CVE-2003-0107 in zlib
Summary
by MITRE
Buffer overflow in the gzprintf function in zlib 1.1.4, when zlib is compiled without vsnprintf or when long inputs are truncated using vsnprintf, allows attackers to cause a denial of service or possibly execute arbitrary code.
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Analysis
by VulDB Data Team • 08/25/2025
The vulnerability identified as CVE-2003-0107 represents a critical buffer overflow flaw within the zlib compression library version 1.1.4. This issue specifically affects the gzprintf function which is responsible for formatted output operations in compressed data streams. The vulnerability arises from improper handling of input data sizes within the compression library's internal buffer management mechanisms. When zlib is compiled in configurations lacking proper vsnprintf support or when long input strings are artificially truncated through vsnprintf operations, the system fails to adequately validate buffer boundaries before writing data. This fundamental flaw creates an exploitable condition where malicious input can exceed allocated buffer space, leading to memory corruption that can be leveraged by attackers to disrupt system operations or potentially gain unauthorized code execution privileges.
The technical nature of this vulnerability aligns with CWE-121, which describes buffer overflow conditions where insufficient space is allocated for data, and CWE-125, which covers out-of-bounds read operations. The flaw operates at the intersection of memory management and input validation, where the gzprintf function fails to properly check the length of formatted strings against available buffer capacity. When attackers provide carefully crafted input strings that exceed the expected buffer limits, the overflow can overwrite adjacent memory locations including return addresses, function pointers, or other critical control data. This type of vulnerability falls under the ATT&CK technique T1499.004, which involves network denial of service through resource exhaustion or memory corruption, and potentially maps to T1059.007 for command and scripting interpreter execution if the overflow leads to code execution.
The operational impact of CVE-2003-0107 extends beyond simple denial of service scenarios to encompass potential remote code execution capabilities depending on system configuration and memory layout. Systems utilizing zlib 1.1.4 in applications such as web servers, file compression utilities, or network protocols that rely on gzip compression are particularly vulnerable. The vulnerability can be exploited through various attack vectors including malformed compressed files, network traffic containing compressed data, or applications that process untrusted input through the affected zlib functions. The severity classification of this vulnerability is heightened by its potential for arbitrary code execution, making it a critical concern for system administrators and security professionals responsible for maintaining software integrity across enterprise environments.
Mitigation strategies for CVE-2003-0107 primarily involve immediate software updates to zlib versions that address the buffer overflow conditions through proper input validation and buffer boundary checks. Organizations should prioritize upgrading to zlib 1.2.0 or later versions where the vulnerability has been resolved through enhanced buffer management and input validation mechanisms. Additionally, implementing proper input sanitization at application layers can provide additional defense-in-depth measures. Security configurations should include disabling unnecessary compression features where possible, implementing strict input length validation for compressed data, and monitoring system logs for unusual compression-related activities. Network segmentation and access controls can help limit the potential impact of exploitation attempts, while regular security assessments should verify that all zlib-dependent applications have been properly updated and configured to prevent exploitation of this vulnerability.