CVE-2026-81881 in radare2
Summary
by MITRE • 09/22/2026
radare2 is a UNIX-like reverse engineering framework and command-line toolset. Prior to 6.2.0, radare2's Mach-O Swift field-metadata parser was vulnerable because a relative Swift field pointer could be lower than the field-metadata section base, making subtraction produce a negative logical index. The vulnerability is triggered by parsing Swift type and class metadata from a crafted Mach-O file. The derived index was used to read four bytes immediately before the allocated field-metadata buffer. This can cause incorrect metadata processing or process termination; no attacker-observable memory disclosure has been demonstrated. This issue is fixed in version 6.2.0.
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Analysis
by VulDB Data Team • 09/22/2026
The vulnerability identified in radare2, a widely used UNIX-like reverse engineering framework and command-line toolset, stems from an improper validation of relative pointers within the Mach-O Swift field-metadata parser prior to version 6.2.0. Radare2 is frequently employed by security professionals for binary analysis, including the disassembly and decompilation of executables compiled with Apple's Swift language. The specific flaw resides in how the tool handles metadata structures embedded within Mach-O files, which are the standard executable format on macOS and iOS platforms. When radare2 processes a crafted Mach-O file containing Swift type or class metadata, it attempts to parse field information by calculating offsets relative to the base of the field-metadata section. The core technical deficiency is that the parser fails to verify whether the calculated relative pointer remains within valid bounds before performing arithmetic operations on these indices.
Specifically, if a maliciously constructed Mach-O file contains a Swift field pointer value that results in an index lower than zero when subtracted from the section base address, the resulting logical index becomes negative due to integer underflow or improper signedness handling. In C-based systems like radare2, using such a negative offset as an array index typically wraps around to a very large positive number if treated as unsigned, or accesses memory immediately preceding the allocated buffer if handled in a way that allows reading before the start of the allocation. In this instance, the vulnerability manifests when the derived invalid index is used to read four bytes from memory located just before the field-metadata buffer. This out-of-bounds read constitutes an improper input validation error where boundary checks are either missing or incorrectly implemented for relative pointer arithmetic involving metadata sections.
From a security classification perspective, this issue aligns with CWE-125: Out-of-Bounds Read, as it involves accessing memory outside of the intended buffer boundaries. Furthermore, because radare2 is an interactive analysis tool often used to inspect untrusted binaries provided by external sources or extracted from potentially compromised systems, this vulnerability falls under ATT&CK technique T1083: File and Directory Discovery, specifically in the context of analyzing file structures for malicious intent. While the immediate impact described does not include direct memory disclosure that an attacker could observe, such as leaking sensitive keys or credentials through side channels, it poses significant risks to system stability and analysis integrity. The incorrect metadata processing can lead to misinterpretation of binary structures, potentially causing the reverse engineer to draw false conclusions about the code's behavior. More critically, the potential for process termination indicates a denial-of-service vector where loading a specially crafted file could crash the radare2 instance, disrupting ongoing forensic or malware analysis workflows.
The operational impact extends beyond simple crashes. In complex reverse engineering scenarios, incorrect parsing of Swift metadata can corrupt subsequent analyses that rely on accurate type information. This may lead to flawed decompilation results or missed insights into application logic, which is particularly dangerous when analyzing security-critical software like operating system components or enterprise applications. Although no attacker-observable memory disclosure has been demonstrated in this specific context, the underlying mechanism of reading arbitrary bytes adjacent to a buffer remains a fundamental flaw that could theoretically be exploited if combined with other vulnerabilities or if the surrounding memory layout changes in different execution environments. The lack of robust bounds checking on relative pointers is a common pitfall in low-level binary parsers and highlights the necessity for rigorous validation of all offset calculations derived from untrusted input data.
To mitigate this vulnerability, users must upgrade radare2 to version 6.2.0 or later, where the developers have implemented proper checks to ensure that calculated indices remain within valid positive bounds before accessing memory. For organizations relying on older versions due to compatibility constraints with legacy scripts or plugins, it is advisable to isolate the execution environment using sandboxing techniques and avoid processing untrusted Mach-O files until an upgrade can be performed. Additionally, implementing static analysis tools configured to detect similar out-of-bounds read patterns in custom parsers can help prevent recurrence of such issues during future development cycles. Security teams should also consider integrating fuzzing strategies targeting binary format parsers as part of their continuous integration pipelines to catch edge cases involving malformed metadata structures before they reach production environments.