CVE-2011-3627 in ClamAV
Summary
by MITRE
The bytecode engine in ClamAV before 0.97.3 allows remote attackers to cause a denial of service (crash) via vectors related to "recursion level" and (1) libclamav/bytecode.c and (2) libclamav/bytecode_api.c.
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Analysis
by VulDB Data Team • 01/05/2025
The vulnerability identified as CVE-2011-3627 represents a critical denial of service weakness in ClamAV's bytecode execution engine prior to version 0.97.3. This flaw specifically targets the recursive processing mechanisms within the antivirus software's bytecode handling components, creating a scenario where maliciously crafted bytecode could trigger system instability. The vulnerability affects the core processing logic that manages recursion levels during bytecode execution, fundamentally compromising the stability of the scanning engine.
The technical implementation of this vulnerability resides in two primary source files within ClamAV's codebase: libclamav/bytecode.c and libclamav/bytecode_api.c. These modules handle the interpretation and execution of bytecode patterns that allow ClamAV to detect complex malware behaviors through custom rules. The recursion level handling mechanism fails to properly validate or limit the depth of recursive calls that can be made during bytecode processing, creating a path for attackers to exhaust system resources through carefully constructed malicious bytecode sequences. This flaw operates at the intersection of software engineering practices and security controls, where insufficient input validation leads to resource exhaustion.
From an operational standpoint, this vulnerability enables remote attackers to cause complete system crashes of ClamAV scanning processes without requiring authentication or elevated privileges. The impact extends beyond simple service disruption to potentially affect entire network security infrastructures that rely on ClamAV for malware detection. When exploited, the vulnerability can cause the antivirus engine to crash repeatedly, leading to service unavailability and potential denial of security monitoring capabilities. Organizations using affected ClamAV versions face significant risk of operational disruption, particularly in environments where real-time scanning is critical for security operations.
The vulnerability aligns with CWE-674, which addresses "Uncontrolled Recursion" in software systems, and demonstrates how improper resource management can lead to system instability. From an attacker's perspective, this represents a low-effort, high-impact vector that can be exploited through the submission of malicious bytecode patterns to ClamAV's processing engine. The ATT&CK framework categorizes this as a Denial of Service technique under the T1499 category, specifically targeting the availability of system services. Organizations should prioritize immediate patching of ClamAV installations to address this vulnerability, while also implementing monitoring for unusual system behavior that might indicate exploitation attempts. The fix implemented in ClamAV 0.97.3 involves enhanced recursion depth controls and improved validation mechanisms within the bytecode processing modules to prevent excessive resource consumption and system instability.