CVE-2011-10029 in Solar FTP Server
Summary
by MITRE • 08/20/2025
Solar FTP Server fails to properly handle format strings passed to the USER command. When a specially crafted string containing format specifiers is sent, the server crashes due to a read access violation in the __output_1() function of sfsservice.exe. This results in a denial of service (DoS) condition.
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Analysis
by VulDB Data Team • 08/20/2025
The vulnerability identified as CVE-2011-10029 represents a critical format string vulnerability within the Solar FTP Server implementation that directly impacts the server's stability and availability. This flaw exists in the handling of user authentication commands where the server fails to properly validate or sanitize input parameters before processing them through format string operations. The issue specifically manifests when the USER command receives a maliciously crafted string containing format specifiers such as %s, %d, or other printf-style formatting characters. The vulnerability stems from the server's insecure use of user-provided input in format string functions without proper input validation or sanitization mechanisms.
The technical exploitation of this vulnerability occurs through the deliberate injection of format specifiers into the USER command parameter, which then gets processed by the sfsservice.exe executable. When the server attempts to process this malformed input, it triggers a read access violation within the __output_1() function, causing the application to crash and terminate unexpectedly. This crash represents a classic buffer overflow scenario where the format string vulnerability allows an attacker to manipulate memory access patterns and potentially execute arbitrary code or cause system instability. The vulnerability operates at the application level and specifically targets the server's authentication handling mechanism, making it particularly dangerous as it can be exploited by unauthorized users to disrupt legitimate service operations.
The operational impact of this vulnerability extends beyond simple denial of service conditions as it can be leveraged to cause persistent service disruptions and potentially provide attackers with opportunities to escalate privileges or gain unauthorized access to the system. The crash occurs in the core service executable which means that the entire FTP service becomes unavailable until manual intervention or system restart occurs. This type of vulnerability aligns with CWE-134 which specifically addresses the use of format strings without proper validation, and represents a significant concern for organizations relying on Solar FTP Server for file transfer operations. The vulnerability can be exploited remotely by any user with access to the FTP service, making it particularly dangerous in environments where the service is exposed to the internet.
Mitigation strategies for this vulnerability should focus on immediate patching of the affected software version and implementation of proper input validation mechanisms. Organizations should ensure that all user input to format string functions is properly sanitized and validated before processing, implementing proper parameter checking and string formatting practices. The solution involves updating the Solar FTP Server to a patched version that properly handles format string operations or implementing application-level protections that prevent malicious format specifiers from being processed. Additionally, network-level protections such as firewall rules and access controls should be implemented to restrict access to the FTP service where possible. This vulnerability demonstrates the importance of following secure coding practices and adheres to ATT&CK technique T1499 which covers network denial of service attacks, and specifically addresses the use of format string vulnerabilities as a method for service disruption and potential privilege escalation.