CVE-2011-5033 in Configserver Security Firewall
Summary
by MITRE
Stack-based buffer overflow in CFS.c in ConfigServer Security & Firewall (CSF) before 5.43, when running on a DirectAdmin server, allows local users to cause a denial of service (crash) via a long string in an admin.list file.
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Analysis
by VulDB Data Team • 08/11/2024
The vulnerability identified as CVE-2011-5033 represents a critical stack-based buffer overflow flaw within the ConfigServer Security & Firewall (CSF) component known as CFS.c. This vulnerability specifically affects versions of CSF prior to 5.43 and manifests when the software operates in conjunction with DirectAdmin server environments. The flaw occurs during the processing of administrative configuration files, particularly when handling data within the admin.list file that contains excessively long string inputs. The buffer overflow vulnerability arises from inadequate input validation and bounds checking mechanisms within the CFS.c module, which fails to properly sanitize or limit the length of strings processed from the admin.list file. This fundamental weakness in input handling creates an exploitable condition where maliciously crafted long strings can overwrite adjacent memory locations on the stack, leading to unpredictable program behavior and potential system instability.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it creates a pathway for local users to potentially escalate their privileges or cause system crashes that could disrupt critical server operations. When a local attacker provides a sufficiently long string within the admin.list file, the overflow can corrupt stack memory, leading to program termination, memory corruption, or in more severe cases, arbitrary code execution depending on the system configuration and memory layout. The vulnerability specifically targets the DirectAdmin server environment, indicating that the exploitation vector is tied to the interaction between CSF and DirectAdmin's administrative interfaces, making it particularly relevant for hosting providers and system administrators who rely on these specific combinations of software. This type of vulnerability falls under CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue that has been consistently identified as a major source of security vulnerabilities in system software and applications.
The exploitation of this vulnerability requires local system access, making it a local privilege escalation vector that can be leveraged by users who already have access to the system but lack administrative privileges. Attackers can utilize this flaw to cause service disruptions, potentially leading to complete system crashes that affect multiple services running on the compromised server. From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', and T1499, which addresses 'Endpoint Denial of Service'. The attack surface is limited to systems where both DirectAdmin and CSF are installed and configured, but this combination is prevalent in shared hosting environments and managed server deployments, making the vulnerability particularly concerning for service providers. The vulnerability demonstrates the importance of proper input validation and memory management practices in security-critical software components, especially those that handle administrative configuration data. Organizations should prioritize updating to CSF version 5.43 or later, which includes patches addressing this specific buffer overflow condition, while also implementing additional security measures such as monitoring for unusual file modifications and restricting local access to sensitive configuration files to minimize potential exploitation risks.