CVE-2018-25018 in UnRAR
Summary
by MITRE • 07/01/2021
UnRAR 5.6.1.7 through 5.7.4 and 6.0.3 has an out-of-bounds write during a memcpy in QuickOpen::ReadRaw when called from QuickOpen::ReadNext.
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Analysis
by VulDB Data Team • 07/04/2021
The vulnerability identified as CVE-2018-25018 represents a critical out-of-bounds write condition affecting multiple versions of the UnRAR library. This flaw exists within the QuickOpen::ReadRaw function which is invoked by QuickOpen::ReadNext, creating a scenario where maliciously crafted archive files can trigger memory corruption. The issue stems from insufficient bounds checking during memory operations, specifically when the memcpy function processes data without proper validation of buffer limits. The vulnerability affects UnRAR versions ranging from 5.6.1.7 through 5.7.4 and includes version 6.0.3, indicating a sustained period of exposure across multiple release cycles. This type of vulnerability falls under the CWE-787 category, which specifically addresses out-of-bounds write conditions that can lead to arbitrary code execution or system compromise.
The technical exploitation of this vulnerability occurs when an attacker crafts a specially formatted RAR archive file that triggers the problematic code path within the UnRAR library. During the QuickOpen::ReadRaw operation, the library attempts to copy data using memcpy without verifying that the source data length matches the destination buffer capacity. This creates an opportunity for attackers to manipulate memory layout and potentially execute malicious code. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1059.007, where adversaries leverage software vulnerabilities to execute arbitrary code through legitimate system processes. The memory corruption can manifest in various ways including application crashes, data corruption, or more severe exploitation scenarios depending on the execution environment and memory layout.
The operational impact of CVE-2018-25018 extends beyond simple denial of service conditions to encompass potential remote code execution capabilities. Systems that utilize UnRAR for archive processing, including web applications, email servers, and file processing services, become vulnerable to attack vectors that could allow adversaries to gain unauthorized access or disrupt operations. The vulnerability affects not only the immediate target application but also any system that relies on UnRAR for decompression operations, creating a wide attack surface. Organizations implementing security controls should consider this vulnerability as part of their broader threat landscape, particularly in environments where untrusted archive files are processed automatically without proper validation. The vulnerability's persistence across multiple versions suggests that defensive measures should include comprehensive patch management strategies and runtime protections that can detect and prevent exploitation attempts.
Mitigation strategies for CVE-2018-25018 should focus on immediate patching of affected UnRAR versions to the latest stable releases that contain the necessary fixes. Organizations should implement additional protective measures including input validation for archive files, sandboxed processing environments, and runtime monitoring for suspicious memory access patterns. The implementation of address space layout randomization and other exploit mitigation techniques can provide additional defense in depth. Security teams should also conduct thorough vulnerability assessments to identify all systems and applications that depend on UnRAR libraries, ensuring comprehensive remediation efforts. Regular security testing and code review processes should be implemented to identify similar patterns in other library components that might present analogous vulnerabilities. The remediation process should include monitoring for exploitation attempts and establishing incident response procedures specifically tailored to handle out-of-bounds write vulnerabilities in archive processing systems.