CVE-2026-119719 in Blender
Summary
by MITRE • 10/30/2026
Blender before 4.5.15 and 5.x before 5.2.3 contains a heap buffer overflow vulnerability in the blend file thumbnail extractor caused by 32-bit integer overflow in thumb_data_vertical_flip(). Attackers can craft a .blend file with malicious TEST block dimensions that trigger an out-of-bounds write when blender-thumbnailer or the Windows shell extension previews it, causing crashes or code execution.
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Analysis
by VulDB Data Team • 10/30/2026
The vulnerability identified involves a critical heap buffer overflow within Blender versions prior to 4.5.15 and 5.x prior to 5.2.3, specifically located in the blend file thumbnail extraction component. This flaw is triggered by a 32-bit integer arithmetic error during the processing of image data for thumbnails. The core technical issue resides in the thumb_data_vertical_flip function, which handles the manipulation of pixel data when generating preview images for .blend files. When an attacker crafts a malicious Blender project file containing specially constructed TEST block dimensions, they can induce an underflow or overflow condition that results in incorrect memory allocation calculations. This miscalculation leads to a heap buffer overflow where subsequent write operations exceed the bounds of the allocated memory region. The vulnerability is particularly dangerous because it affects both the standalone blender-thumbnailer utility and the Windows shell extension used for file previewing, meaning exploitation can occur simply by viewing a folder containing the malicious file in standard operating system interfaces without necessarily opening Blender itself.
From an operational perspective, this vulnerability poses significant risks to user systems that rely on automated thumbnail generation or visual previews of 3D project files. The immediate impact includes application crashes due to memory corruption, which disrupts workflow and can lead to data loss if unsaved work is affected. More critically, the out-of-bounds write capability allows for potential arbitrary code execution. An attacker who can trick a user into previewing or opening such a file could execute malicious payloads with the privileges of the current user process. This represents a classic attack vector where trusted software components are abused to bypass security boundaries. The reliance on integer overflow as the root cause highlights common pitfalls in C/C++ memory management, particularly when handling external input without rigorous bounds checking before arithmetic operations or buffer allocations.
This vulnerability aligns with CWE-190 Integer Overflow or Wraparound and CWE-787 Out-of-bounds Write within the Common Weakness Enumeration framework. In terms of tactical mapping to the MITRE ATT&CK matrix, this exploit technique falls under Tactic TA0004 Privilege Escalation and Technique T1203 Exploitation for Client Execution, as it targets client-side applications through file preview mechanisms often found in operating system shells like Windows Explorer. The attack chain typically involves social engineering or supply chain compromise to distribute the malicious .blend file, followed by automatic execution via shell extensions that generate thumbnails on demand. This passive exploitation method is highly effective because users rarely suspect standard file previews as a vector for code execution.
Mitigation strategies must prioritize immediate software updates to the patched versions of Blender mentioned above. For environments where updating is not immediately feasible, administrators should disable thumbnail generation for .blend files in Windows shell extensions or configure antivirus solutions to block access to suspiciously crafted binary structures within 3D file formats. Additionally, developers implementing similar image processing logic should enforce strict validation of input dimensions before performing arithmetic operations and ensure that buffer sizes are calculated with overflow-safe functions such as checked addition routines. Implementing Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP) can also mitigate the success rate of code execution attempts by making it harder to predict memory layouts, although these controls do not prevent the initial vulnerability from being triggered.