CVE-2021-32494 in Radare2
Summary
by MITRE • 07/07/2023
Radare2 has a division by zero vulnerability in Mach-O parser's rebase_buffer function. This allow attackers to create malicious inputs that can cause denial of service.
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Analysis
by VulDB Data Team • 07/25/2023
The CVE-2021-32494 vulnerability represents a critical division by zero flaw within the Radare2 reverse engineering framework's Mach-O file parser implementation. This vulnerability specifically affects the rebase_buffer function which processes Mach-O binary files commonly used on macOS and iOS systems. The flaw occurs when the parser encounters malformed Mach-O structures that trigger a division operation with a zero denominator, causing the application to crash and resulting in a denial of service condition. The vulnerability demonstrates a classic programming error where input validation fails to account for edge cases in binary file parsing, particularly when dealing with malformed rebase information within Mach-O headers.
The technical implementation of this vulnerability stems from improper error handling within the Mach-O parser's rebase_buffer function which lacks adequate checks for zero values during division operations. When processing maliciously crafted Mach-O files, attackers can construct inputs that cause the division operation to execute with a zero divisor, leading to an immediate crash of the Radare2 application. This type of vulnerability falls under CWE-369, which specifically addresses the division by zero error condition that occurs when a program attempts to divide by zero, resulting in a program crash or abnormal termination. The flaw represents a fundamental lack of input sanitization and error handling that is essential when processing untrusted binary data from external sources.
From an operational perspective, this vulnerability poses significant risks to security researchers and analysts who rely on Radare2 for binary analysis. The denial of service condition can be exploited by adversaries to disrupt legitimate analysis workflows, potentially preventing security professionals from examining malicious files or conducting forensic investigations. The impact extends beyond simple service disruption as it can be leveraged in broader attack chains where attackers might use this vulnerability to prevent security tools from functioning properly. The vulnerability affects all versions of Radare2 that implement the Mach-O parser, making it particularly concerning for environments where automated analysis systems depend on this tool for processing potentially malicious binaries. This type of vulnerability aligns with ATT&CK technique T1497 which covers virtualization and sandbox evasion through system manipulation.
The mitigation strategy for CVE-2021-32494 requires immediate patching of Radare2 installations to address the division by zero condition in the rebase_buffer function. Security teams should implement defensive measures including input validation for Mach-O files and network segmentation to limit exposure to potentially malicious inputs. Additionally, organizations should consider implementing alternative binary analysis tools as a backup measure while patches are deployed. The fix should include proper validation of division operands before execution, ensuring that zero values are rejected or handled gracefully within the parser implementation. Regular security updates and vulnerability assessments should be conducted to prevent similar issues in other components of the reverse engineering toolchain. Organizations using Radare2 in production environments must prioritize this patch to maintain system availability and prevent potential exploitation by threat actors seeking to disrupt security analysis operations.