CVE-2004-2533 in Serv-U
Summary
by MITRE
Serv-U FTP Server 4.1 (possibly 4.0) allows remote attackers to cause a denial of service (application crash) via a SITE CHMOD command with a "\\...\" followed by a short string, causing partial memory corruption, a different vulnerability than CVE-2004-2111.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 05/25/2019
The vulnerability identified as CVE-2004-2533 affects the Serv-U FTP Server version 4.1 and potentially 4.0, representing a critical denial of service flaw that can be exploited remotely by attackers. This vulnerability specifically manifests through the improper handling of the SITE CHMOD command, which is a standard ftp command used to change file permissions. The attack vector involves sending a malformed SITE CHMOD command that consists of a backslash character followed by three dots and another backslash, succeeded by a short string. This particular sequence triggers a memory corruption issue within the server's processing mechanism, ultimately leading to application instability and potential crash.
The technical flaw stems from inadequate input validation and memory management within the Serv-U FTP server implementation. When the server receives the malformed SITE CHMOD command, it fails to properly sanitize the input string before processing it, resulting in partial memory corruption. This type of vulnerability falls under the category of buffer overflows or memory corruption issues that are commonly classified as CWE-121, which deals with stack-based buffer overflows, or more specifically CWE-787, which addresses out-of-bounds write operations. The memory corruption occurs during the parsing and execution of the command, where the server's internal structures become compromised, leading to unpredictable behavior and eventual application termination.
From an operational impact perspective, this vulnerability presents significant risks to organizations relying on Serv-U FTP servers for file transfer operations. The remote exploitation capability means that attackers can potentially disrupt services without requiring physical access or local privileges, making it particularly dangerous for systems hosting sensitive data or critical business operations. The denial of service condition can result in complete service interruption, preventing legitimate users from accessing files through the ftp server, which can lead to business disruption, data accessibility issues, and potential financial losses. Organizations may also face reputational damage if such attacks result in extended service outages or compromise the availability of their ftp services.
The vulnerability demonstrates characteristics consistent with the ATT&CK framework's privilege escalation and denial of service techniques, specifically mapping to the T1499.004 sub-technique related to network denial of service. Security professionals should note that this issue represents a distinct vulnerability from CVE-2004-2111, indicating that multiple memory corruption flaws exist within the same software version. Organizations should implement immediate mitigations including applying vendor patches, implementing network segmentation to limit access to ftp services, and monitoring for suspicious SITE CHMOD command patterns in their ftp server logs. The remediation process should involve thorough testing of patches to ensure they do not introduce compatibility issues with existing ftp operations while maintaining the server's core functionality. Additionally, network administrators should consider implementing intrusion detection systems that can identify and alert on anomalous ftp command sequences that match the vulnerability pattern described in CVE-2004-2533.