CVE-2006-6940 in OWA
Summary
by MITRE
Buffer overflow in the ParseHeader function in clsOWA.cls in POP3/SMTP to OWA (pop2owa) 1.1.3 allows remote attackers to execute arbitrary code via a long header in an e-mail message.
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Analysis
by VulDB Data Team • 08/17/2018
The vulnerability described in CVE-2006-6940 represents a critical buffer overflow flaw within the pop2owa component of Microsoft Office Web Access, specifically affecting versions 1.1.3 and earlier. This vulnerability exists within the ParseHeader function of the clsOWA.cls file, which processes incoming email messages from POP3 and SMTP servers and forwards them to Office Web Access for display. The flaw arises when the system processes email headers that exceed the allocated buffer space, creating an exploitable condition that can be leveraged by remote attackers to execute arbitrary code on the affected system.
The technical implementation of this vulnerability stems from inadequate input validation and buffer management within the email parsing routine. When an attacker crafts an email message containing an excessively long header field, the ParseHeader function fails to properly check the length of the incoming data against the predefined buffer boundaries. This allows the malicious input to overflow into adjacent memory locations, potentially overwriting critical program variables, return addresses, or executable code segments. The vulnerability specifically affects the pop2owa component which serves as a bridge between email servers and the web-based Outlook interface, making it a prime target for attackers seeking to compromise email infrastructure.
From an operational perspective, this vulnerability presents a significant threat to organizations relying on Office Web Access for email services, as it enables remote code execution without requiring authentication. Attackers can exploit this flaw by simply sending a specially crafted email message to an affected system, making the attack vector particularly dangerous for email servers that process messages from untrusted sources. The impact extends beyond simple code execution, as successful exploitation could lead to complete system compromise, data exfiltration, or the establishment of persistent backdoors within the email infrastructure. Organizations using older versions of Office Web Access are particularly vulnerable since this flaw was not patched in the affected releases, leaving them exposed to potential exploitation.
The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and demonstrates characteristics consistent with the attack patterns documented in the MITRE ATT&CK framework under the technique of code injection. Organizations should implement immediate mitigations including applying the vendor-provided security patches, restricting email traffic from untrusted sources, implementing email header length validation, and monitoring for suspicious email patterns. Additionally, network segmentation and intrusion detection systems should be configured to detect potential exploitation attempts, while regular security assessments should be conducted to identify similar vulnerabilities in other components of the email infrastructure. The remediation approach should also include updating to supported versions of Office Web Access and implementing proper input validation mechanisms throughout the email processing pipeline to prevent similar buffer overflow conditions from occurring in other components.