CVE-2026-81885 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 NE relocation fixup-chain parser was vulnerable because the NE relocation parser followed fixup chains without an active iteration limit or cycle detection. The vulnerability is triggered by opening a crafted NE executable whose in-bounds relocation entry points back to itself instead of reaching 0xffff. The parser repeatedly processed the same relocation and allocated another relocation object on each iteration. This can cause denial of service through continuous CPU and memory consumption. This issue is fixed in version 6.2.0.
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Analysis
by VulDB Data Team • 09/22/2026
radare2 serves as a comprehensive UNIX-like reverse engineering framework and command-line toolset, widely utilized by security professionals for binary analysis and disassembly. Within this ecosystem, the handling of New Executable (NE) format files is critical for analyzing legacy Windows applications and certain embedded systems. The NE relocation fixup-chain parser plays a specific role in resolving address references within these binaries, ensuring that code pointers are correctly adjusted based on their load addresses. However, prior to version 6.2.0, this component contained a significant logic flaw related to how it traversed chains of relocations during the parsing process.
The core technical vulnerability stems from an absence of active iteration limits or cycle detection mechanisms within the NE relocation parser. When processing a crafted NE executable containing maliciously constructed relocation entries, the parser would follow fixup chains without verifying whether those chains had been previously visited. Specifically, if an in-bounds relocation entry pointed back to itself rather than terminating with the expected end-of-chain marker value of 0xffff, the parser entered an infinite loop. This lack of boundary checking allowed a single maliciously crafted file to trigger continuous processing by the application engine.
During this infinite traversal, the parser repeatedly processed the same relocation data and allocated new relocation objects on each iteration without freeing previous allocations or breaking out of the cycle. This behavior resulted in unbounded memory consumption as the heap filled with redundant object instances. Simultaneously, the CPU was consumed at a high rate due to the continuous execution of the parsing logic. The operational impact is primarily a denial of service condition, where radare2 becomes unresponsive and eventually crashes or consumes all available system resources when attempting to open such crafted files. This represents a classic resource exhaustion vulnerability that can be exploited by an attacker providing a malicious binary file for analysis.
From a classification perspective, this flaw aligns with CWE-789: Uncontrolled Memory Allocation, as the application fails to limit the amount of memory consumed during processing. It also relates to CWE-835: Loop with Unreachable Exit Condition due to logical errors in cycle detection. In terms of offensive security frameworks, this vulnerability could be leveraged within ATT&CK technique T1496: Resource Hijacking, where an attacker uses compromised or malicious resources to disrupt service availability for legitimate users or analysts.
The issue was addressed in version 6.2.0 by implementing proper cycle detection and iteration limits within the NE relocation parser. Developers integrating radare2 into automated pipelines should ensure they are using this patched version to prevent potential denial of service attacks through malformed binary inputs. Mitigation strategies include validating input files before processing, applying resource usage quotas where possible, and keeping the reverse engineering tools updated with the latest security patches provided by the maintainers.