CVE-2004-2026 in Pound
Summary
by MITRE
Format string vulnerability in the logmsg function in svc.c for Pound 1.5 and earlier allows remote attackers to execute arbitrary code via format string specifiers in syslog messages.
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Analysis
by VulDB Data Team • 07/06/2025
The vulnerability identified as CVE-2004-2026 represents a critical format string flaw within the Pound load balancer version 1.5 and earlier. This issue resides in the logmsg function located within the svc.c source file, where improper handling of user-supplied input leads to potential remote code execution. The vulnerability specifically manifests when the application processes syslog messages containing format string specifiers, creating an avenue for malicious actors to exploit the software's logging mechanism.
The technical exploitation of this vulnerability stems from the application's failure to properly sanitize or validate input parameters before passing them to printf-style functions. When Pound receives syslog messages containing format specifiers such as %s, %d, or %x, the logmsg function processes these without adequate protection, allowing attackers to inject malicious format specifiers that can trigger unintended behavior. This flaw directly maps to CWE-134, which specifically addresses the use of user-controlled format strings in functions like printf, sprintf, and related formatting routines. The vulnerability enables attackers to manipulate the program's execution flow by controlling how format specifiers are interpreted during string formatting operations.
The operational impact of CVE-2004-2026 extends beyond simple code execution to encompass potential system compromise and data exfiltration capabilities. Remote attackers can leverage this vulnerability to execute arbitrary code with the privileges of the Pound process, which typically runs with elevated permissions to manage network services. The attack vector requires the attacker to send specially crafted syslog messages to the Pound service, making it particularly dangerous in environments where syslog messages are accepted from untrusted sources. This vulnerability can lead to complete system compromise, allowing attackers to gain persistent access, install backdoors, or escalate privileges to root level access depending on the system configuration and execution context.
Mitigation strategies for this vulnerability involve multiple layers of defense to protect against exploitation. The primary and most effective solution is to upgrade to Pound version 1.6 or later, where the format string vulnerability has been addressed through proper input validation and sanitization of log messages. System administrators should also implement network segmentation to limit access to the Pound service, ensuring that only trusted sources can send syslog messages to the application. Additionally, configuring the system to use non-format string functions for logging operations or implementing strict input validation on all syslog message content can provide additional protection. Organizations should also consider implementing intrusion detection systems to monitor for suspicious syslog message patterns that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1059.007, which covers the use of command and scripting interpreter for execution, as successful exploitation would likely involve executing malicious code through the compromised logging mechanism.