CVE-2006-0559 in WebShield SMTP
Summary
by MITRE
Format string vulnerability in the SMTP server for McAfee WebShield 4.5 MR2 and earlier allows remote attackers to execute arbitrary code via format strings in the domain name portion of a destination address, which are not properly handled when a bounce message is constructed.
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Analysis
by VulDB Data Team • 06/22/2025
The vulnerability identified as CVE-2006-0559 represents a critical format string vulnerability within the SMTP server component of McAfee WebShield 4.5 MR2 and earlier versions. This flaw resides in the handling of domain name portions within email destination addresses during the construction of bounce messages, creating a pathway for remote code execution. The vulnerability specifically manifests when the system processes malformed format specifiers within the domain portion of email addresses, which are not adequately sanitized or escaped during the bounce message generation process.
This vulnerability falls under CWE-134, which specifically addresses the use of format strings without proper validation or sanitization. The technical implementation flaw occurs in the SMTP server's bounce message construction logic where user-supplied domain names containing format specifiers such as %s, %d, or %x are directly incorporated into the message template without proper input validation. When an attacker crafts a malicious email address with carefully constructed format specifiers in the domain portion, the SMTP server processes these without adequate safeguards, leading to potential memory corruption and arbitrary code execution.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass potential system compromise and data breach scenarios. Attackers can leverage this vulnerability to execute arbitrary commands with the privileges of the SMTP service account, potentially leading to full system compromise if the service runs with elevated privileges. The remote nature of the attack means that exploitation can occur from any location without requiring physical access or prior authentication, making it particularly dangerous in networked environments. This vulnerability specifically targets the email security infrastructure, potentially allowing attackers to bypass security controls and gain unauthorized access to email communications.
The attack surface for this vulnerability is significant within organizations relying on McAfee WebShield for email security, particularly in environments where email servers are directly exposed to external networks. The exploitation process typically involves sending a specially crafted email with a malicious domain name containing format specifiers, which triggers the vulnerable code path during bounce message generation. This attack vector aligns with ATT&CK technique T1190, which describes the use of vulnerabilities in software to execute malicious code. Organizations should implement immediate mitigations including applying the vendor-provided patches, restricting external email access to the vulnerable system, and monitoring for suspicious email traffic patterns. Network segmentation and firewall rules should be configured to limit exposure of the affected SMTP server to untrusted networks, while regular security assessments should be conducted to identify similar vulnerabilities in other email security products. The vulnerability also underscores the importance of proper input validation and the principle of least privilege in security implementations, as proper sanitization of user inputs could have prevented the exploitation of this format string vulnerability.