CVE-2021-34871 in View
Summary
by MITRE • 01/14/2022
This vulnerability allows remote attackers to execute arbitrary code on affected installations of Bentley View 10.15.0.75. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The specific flaw exists within the parsing of BMP files. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a heap-based buffer. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-14695.
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Analysis
by VulDB Data Team • 01/17/2022
CVE-2021-34871 represents a critical buffer overflow vulnerability affecting Bentley View version 10.15.0.75, classified under CWE-121 as a stack-based buffer overflow due to insufficient input validation during BMP file processing. This vulnerability resides in the image parsing functionality where the application fails to properly validate the length of user-supplied data before copying it to heap-based buffers, creating an exploitable condition that can be leveraged by remote attackers. The flaw specifically manifests when Bentley View processes maliciously crafted BMP files, which can be delivered through web pages or direct file attachments, requiring user interaction to initiate exploitation. The vulnerability operates at the intersection of memory safety and input validation, where the application's failure to implement proper bounds checking allows attackers to overwrite adjacent memory locations, potentially leading to arbitrary code execution within the context of the current process. This type of vulnerability falls under the ATT&CK technique T1203 - Exploitation for Client Execution, as it exploits a software vulnerability to execute malicious code on the target system.
The operational impact of this vulnerability extends beyond simple code execution, as it enables attackers to gain persistent access to systems running vulnerable versions of Bentley View, which is commonly used in engineering and construction environments for viewing and managing technical drawings and documents. Attackers can craft malicious BMP files that, when opened by a victim using the vulnerable software, trigger the buffer overflow condition and allow for privilege escalation or lateral movement within the network. The exploitation process typically involves creating a specially crafted BMP file that contains oversized data structures, which when parsed by the vulnerable application causes the heap buffer to overflow and corrupt adjacent memory regions. This corruption can be manipulated to redirect program execution flow, potentially allowing attackers to inject and execute shellcode or other malicious payloads. The vulnerability's remote exploitability through web-based delivery methods makes it particularly dangerous in enterprise environments where users may inadvertently visit compromised websites or open malicious attachments.
Mitigation strategies for CVE-2021-34871 should focus on immediate patching of the affected Bentley View software to the latest version that includes proper input validation and bounds checking mechanisms. Organizations should implement network-based protections such as web application firewalls and content filtering systems to block access to known malicious domains and files. Additionally, security awareness training for users is essential to prevent accidental interaction with malicious content, particularly through email attachments or web downloads. The vulnerability demonstrates the importance of proper input validation in image processing libraries and highlights the need for defensive programming practices such as implementing stack canaries, address space layout randomization, and other exploit mitigations. System administrators should also consider implementing least privilege principles for the Bentley View application, limiting the damage that can be caused by successful exploitation. Regular vulnerability assessments and penetration testing should be conducted to identify similar issues in other software components, particularly those handling user-supplied binary data in memory-sensitive operations. The ATT&CK framework suggests implementing process monitoring and anomaly detection to identify potential exploitation attempts, as attackers may attempt to leverage this vulnerability as part of broader attack campaigns targeting engineering and construction organizations.