CVE-2007-0855 in WinRar
Summary
by MITRE
Stack-based buffer overflow in RARLabs Unrar, as packaged in WinRAR and possibly other products, allows user-assisted remote attackers to execute arbitrary code via a crafted, password-protected archive.
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Analysis
by VulDB Data Team • 07/14/2019
The vulnerability identified as CVE-2007-0855 represents a critical stack-based buffer overflow flaw within RARLabs Unrar library implementation, which forms the core decompression functionality of WinRAR and numerous other software applications that utilize this compression library. This vulnerability specifically affects the handling of password-protected archive files, creating a dangerous condition where maliciously crafted archive contents can trigger memory corruption during the extraction process. The flaw exists in the way the unrar library processes certain archive structures, particularly when dealing with compressed data that exceeds allocated buffer boundaries, leading to potential memory overwrite conditions that can be exploited by remote attackers.
The technical nature of this vulnerability stems from improper bounds checking within the decompression routines of the unrar library, which operates under the Common Weakness Enumeration framework as CWE-121, representing stack-based buffer overflow conditions. When a maliciously constructed password-protected archive is processed, the library fails to validate the size of incoming data against allocated buffer space, allowing attackers to write beyond the intended memory boundaries. This condition can be exploited through a user-assisted remote attack vector, meaning that an attacker does not need to directly interact with the target system but can rely on a user opening a specially crafted archive file. The attack requires the target to have the unrar library installed and to attempt extraction of the malicious archive, which can occur through various legitimate use cases including email attachments, download files, or web-based content.
The operational impact of this vulnerability extends beyond simple code execution, as it can enable attackers to gain full control over affected systems through the exploitation of the buffer overflow condition. The attack vector operates through the standard decompression process that occurs when users extract files from archives, making it particularly dangerous in enterprise environments where users frequently handle compressed files from external sources. The vulnerability can be leveraged to execute arbitrary code with the privileges of the user running the decompression software, potentially leading to complete system compromise, data exfiltration, or lateral movement within network environments. Security researchers have classified this vulnerability as highly dangerous due to its ease of exploitation and the widespread use of the unrar library across numerous applications and operating systems, creating a significant attack surface for potential adversaries.
Mitigation strategies for CVE-2007-0855 require immediate patching of affected systems and applications that utilize the unrar library, with vendors releasing updated versions that include proper bounds checking and memory validation routines. Organizations should implement comprehensive software inventory management to identify all systems using vulnerable versions of the unrar library, including custom applications, enterprise software, and third-party tools that may incorporate this decompression functionality. Security controls should emphasize user education about the dangers of opening untrusted archive files, particularly those that are password-protected or appear suspicious. Network-based mitigations can include content filtering and sandboxing of archive files before user access, while system-level protections should focus on memory protection mechanisms such as stack canaries, address space layout randomization, and data execution prevention features. The vulnerability demonstrates the critical importance of maintaining up-to-date software libraries and implementing robust software supply chain security measures to prevent exploitation of known vulnerabilities in widely used components. Organizations should also consider implementing automated patch management systems to ensure timely remediation of such critical security flaws, as the long window between vulnerability disclosure and exploitation creates significant risk for unpatched systems.