CVE-2012-3501 in squidclamav
Summary
by MITRE
The squidclamav_check_preview_handler function in squidclamav.c in SquidClamav 5.x before 5.8 and 6.x before 6.7 passes an unescaped URL to a system command call, which allows remote attackers to cause a denial of service (daemon crash) via a URL with certain characters, as demonstrated using %0D or %0A.
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Analysis
by VulDB Data Team • 12/12/2021
The vulnerability identified as CVE-2012-3501 represents a critical security flaw in SquidClamav versions 5.x prior to 5.8 and 6.x prior to 6.7, specifically within the squidclamav_check_preview_handler function in the squidclamav.c file. This issue constitutes a command injection vulnerability that arises from improper input validation and sanitization when processing web URLs. The flaw occurs when the application processes URLs containing certain control characters, particularly those representing carriage return and line feed sequences, which are encoded as %0D and %0A respectively. The vulnerability stems from the function's failure to properly escape or sanitize URL parameters before incorporating them into system command calls, creating an avenue for malicious input to influence command execution.
The technical implementation of this vulnerability involves the improper handling of user-supplied data within a context where system commands are executed. When a malicious URL containing control characters is processed by the squidclamav_check_preview_handler function, these characters are not properly escaped or filtered before being passed to system command execution. This creates a scenario where attackers can inject command sequences that manipulate the execution flow of the underlying system calls, potentially causing the daemon to crash or behave unpredictably. The vulnerability operates at the intersection of input validation failures and command execution contexts, making it particularly dangerous as it can be exploited without authentication and can affect the availability of the service.
The operational impact of CVE-2012-3501 extends beyond simple denial of service to potentially compromising the entire security infrastructure that relies on SquidClamav for content filtering. When exploited, this vulnerability can cause the SquidClamav daemon to crash repeatedly, leading to service unavailability for legitimate users and potentially creating a window for more sophisticated attacks. The daemon crash represents a direct threat to the availability of web content filtering services, which are often critical components in enterprise security architectures. From an attacker's perspective, this vulnerability provides a straightforward method to disrupt services without requiring complex exploitation techniques, making it particularly attractive for malicious actors seeking to cause disruption or gain further access to the network.
This vulnerability maps directly to CWE-78, which describes improper neutralization of special elements used in OS commands, and aligns with ATT&CK technique T1203, which covers "Exploitation for Client Execution" through command injection methods. The attack vector demonstrates a classic command injection flaw where user input flows directly into system command execution without proper sanitization. Organizations implementing SquidClamav should prioritize patching this vulnerability immediately, as the impact extends beyond simple service disruption to potential compromise of the entire filtering infrastructure. Mitigation strategies should include implementing strict input validation, character encoding normalization, and ensuring that all user-supplied data is properly escaped before being used in system command contexts. Additionally, network segmentation and monitoring for unusual daemon crash patterns can help detect exploitation attempts and provide early warning of potential attacks targeting this vulnerability.