CVE-2007-3123 in ClamAV
Summary
by MITRE
unrar.c in libclamav in ClamAV before 0.90.3 and 0.91 before 0.91rc1 allows remote attackers to cause a denial of service (core dump) via a crafted RAR file with a modified vm_codesize value, which triggers a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 07/20/2021
The vulnerability identified as CVE-2007-3123 represents a critical heap-based buffer overflow flaw within the libclamav library component of ClamAV antivirus software. This issue specifically affects the unrar.c module which handles RAR archive file processing, making it particularly dangerous in environments where RAR files are commonly encountered. The vulnerability stems from inadequate input validation mechanisms that fail to properly sanitize the vm_codesize field within crafted RAR archives, allowing malicious actors to exploit this weakness remotely without requiring authentication or privileged access. The flaw exists in ClamAV versions prior to 0.90.3 and 0.91rc1, indicating that this vulnerability was present in widely deployed software versions and could have affected numerous security implementations across various organizations.
The technical exploitation of this vulnerability occurs when a maliciously crafted RAR file is processed by ClamAV, specifically targeting the vm_codesize parameter which controls virtual machine code size within the decompression routine. When this value is modified beyond acceptable bounds, the buffer overflow condition manifests during memory allocation operations, leading to memory corruption that ultimately results in a core dump. This heap-based overflow represents a classic software security flaw that falls under the CWE-121 category of stack-based buffer overflow, though the heap context makes it particularly challenging to predict and exploit. The vulnerability demonstrates poor memory management practices and insufficient bounds checking within the decompression algorithm, creating an avenue for attackers to disrupt service availability through controlled memory corruption.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can be leveraged to cause system instability and potentially provide a foundation for more sophisticated attacks. When a core dump occurs due to the heap overflow, the affected ClamAV process terminates unexpectedly, creating service disruption that can be particularly problematic in enterprise environments where antivirus scanning is critical for security operations. Organizations relying on ClamAV for email filtering, file system scanning, or network traffic inspection may experience significant service degradation or complete service outages when malicious RAR files are processed. The remote exploitability aspect means that attackers can trigger this condition without physical access to systems, making it a particularly attractive target for malicious actors seeking to disrupt security operations or create cover for other attack vectors. This vulnerability aligns with ATT&CK technique T1499.004 which focuses on network denial of service attacks, and demonstrates how decompression-based vulnerabilities can be weaponized for operational disruption.
Mitigation strategies for CVE-2007-3123 primarily involve immediate software updates to ClamAV versions 0.90.3 or 0.91rc1 and later, which contain the necessary patches to address the buffer overflow condition. System administrators should implement comprehensive patch management procedures to ensure all instances of ClamAV are updated across network infrastructure, including email servers, file servers, and endpoint devices. Additional protective measures include implementing network-based filtering to block suspicious RAR files, deploying sandboxing mechanisms for file analysis, and configuring ClamAV to limit resource consumption during archive processing. Organizations should also consider implementing monitoring solutions to detect abnormal process termination patterns that might indicate exploitation attempts. The vulnerability highlights the importance of input validation and memory safety practices in security software, particularly for decompression libraries that handle untrusted data from network sources. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other decompression libraries and security tools that may be subject to similar buffer overflow conditions.