CVE-2008-3658 in PHP
Summary
by MITRE
Buffer overflow in the imageloadfont function in ext/gd/gd.c in PHP 4.4.x before 4.4.9 and PHP 5.2 before 5.2.6-r6 allows context-dependent attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted font file.
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Analysis
by VulDB Data Team • 08/16/2019
The vulnerability described in CVE-2008-3658 represents a critical buffer overflow condition within PHP's GD library implementation that affects multiple PHP versions including 4.4.x before 4.4.9 and 5.2.x before 5.2.6-r6. This flaw exists in the imageloadfont function located in the ext/gd/gd.c source file, which is responsible for loading font files for image processing operations. The vulnerability manifests when PHP processes specially crafted font files that contain malformed data structures, leading to memory corruption issues that can be exploited by malicious actors.
The technical implementation of this buffer overflow stems from inadequate input validation within the font loading mechanism. When PHP's GD extension attempts to parse font files, the imageloadfont function fails to properly bounds-check array accesses and memory allocations during the font data processing phase. This allows attackers to craft font files with oversized or malformed headers that exceed the allocated buffer space, causing stack or heap corruption. The vulnerability is context-dependent because it requires specific conditions to be met, including the execution of PHP code that utilizes the affected image processing functions and the presence of vulnerable font files in the processing path. According to CWE-121, this represents a classic stack-based buffer overflow scenario where insufficient bounds checking leads to memory corruption.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable remote code execution in certain configurations. When exploited successfully, the buffer overflow can cause PHP processes to crash, resulting in service disruption and potential denial of service attacks against web applications. More critically, attackers with sufficient privileges or specific exploitation conditions could leverage this vulnerability to inject and execute arbitrary code on affected systems. The risk is particularly elevated in web environments where PHP applications process user-uploaded content, as attackers could upload malicious font files that trigger the vulnerability when processed by PHP's image handling functions. This vulnerability aligns with ATT&CK technique T1190 which describes the use of buffer overflow vulnerabilities for code execution in web applications.
Mitigation strategies for this vulnerability require immediate patching of affected PHP installations to versions 4.4.9 and 5.2.6-r6 or later, which contain the necessary fixes to prevent the buffer overflow condition. System administrators should also implement strict input validation for all font file processing operations and consider implementing additional security controls such as file type restrictions, content scanning, and sandboxing mechanisms for image processing operations. Network-level defenses should include monitoring for suspicious file upload patterns and implementing web application firewalls that can detect and block attempts to exploit this vulnerability. Organizations should also conduct comprehensive vulnerability assessments to identify all PHP installations within their environment and ensure proper patch management procedures are in place to prevent similar issues in the future. The remediation process should include thorough testing of patched environments to ensure that the fix does not introduce regressions in legitimate image processing functionality while maintaining the security improvements.