CVE-2005-4470 in BlenLoader
Summary
by MITRE
Heap-based buffer overflow in the get_bhead function in readfile.c in Blender BlenLoader 2.0 through 2.40pre allows remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code via a .blend file with a negative bhead.len value, which causes less memory to be allocated than expected, possibly due to an integer overflow.
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Analysis
by VulDB Data Team • 08/02/2019
The vulnerability identified as CVE-2005-4470 represents a critical heap-based buffer overflow in Blender's BlenLoader component affecting versions 2.0 through 2.40pre. This flaw resides within the get_bhead function located in the readfile.c source file, which processes .blend files used by the popular open-source 3D creation software. The vulnerability stems from inadequate input validation when handling the bhead.len field within the file structure, creating a scenario where maliciously crafted .blend files can trigger unexpected memory allocation behavior. The issue manifests when the bhead.len value is negative, causing the application to allocate insufficient memory while the actual data payload requires more space than anticipated. This fundamental mismatch between allocated and required memory creates exploitable conditions that can be leveraged by remote attackers to compromise system integrity. The vulnerability operates at the intersection of memory safety and integer handling, where the negative length value triggers an integer overflow condition that fundamentally alters the memory allocation logic. According to the Common Weakness Enumeration framework, this vulnerability maps to CWE-121, heap-based buffer overflow, and also aligns with CWE-190, integer overflow or wraparound, demonstrating the compound nature of the security flaw.
The operational impact of this vulnerability extends beyond simple denial of service to encompass potential arbitrary code execution capabilities, making it particularly dangerous in remote attack scenarios. When a victim opens a specially crafted .blend file, the application crashes due to memory corruption, but the attacker can potentially leverage the buffer overflow to inject and execute malicious code within the application's memory space. This creates a significant threat vector for attackers who can remotely distribute malicious .blend files through various channels including email attachments, web downloads, or file sharing platforms. The vulnerability's exploitation requires minimal user interaction beyond opening the file, making it particularly effective for social engineering campaigns. The integer overflow condition specifically affects how the application calculates memory requirements for file parsing, where negative values cause the system to allocate insufficient heap space while the actual data payload attempts to write beyond these boundaries. This creates a classic heap corruption scenario that can be exploited using techniques such as return-oriented programming or direct code injection, depending on the target system's memory layout and protection mechanisms.
Mitigation strategies for CVE-2005-4470 must address both the immediate vulnerability and broader security posture of systems using affected Blender versions. The primary remediation involves upgrading to Blender versions 2.40 or later, where the file parsing logic was significantly improved to properly validate bhead.len values and prevent negative length processing. Organizations should implement strict file validation policies that scan .blend files for suspicious structures before allowing them to be processed by the application. Network-level controls including email filtering and web content scanning can help prevent the distribution of malicious .blend files through common attack vectors. The vulnerability demonstrates the importance of input sanitization and proper integer handling in file format parsers, aligning with ATT&CK technique T1059.007 for execution through scripting and T1203 for exploitation of file parsing vulnerabilities. System administrators should also consider implementing application whitelisting policies that restrict execution of untrusted .blend files, particularly in enterprise environments where multiple users may be exposed to potentially malicious content. Memory protection mechanisms such as stack canaries, address space layout randomization, and data execution prevention can provide additional defense-in-depth measures against exploitation attempts. Regular security audits of file processing components and adherence to secure coding practices including bounds checking and proper integer overflow protection should be implemented to prevent similar vulnerabilities in future development cycles.