CVE-2008-7105 in PureMessage for Microsoft Exchange
Summary
by MITRE
Sophos PureMessage for Microsoft Exchange 3.0 before 3.0.2 allows remote attackers to cause a denial of service (EdgeTransport.exe termination) via a TNEF-encoded message with a crafted rich text body that is not properly handled during conversion to plain text. NOTE: this might be related to CVE-2008-7104.
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Analysis
by VulDB Data Team • 08/20/2021
The vulnerability described in CVE-2008-7105 represents a critical denial of service flaw within Sophos PureMessage for Microsoft Exchange software version 3.0 and earlier. This security issue affects organizations that rely on Sophos email security solutions to protect their exchange environments from malicious content. The vulnerability specifically targets the EdgeTransport.exe process which serves as a critical component in the email delivery pipeline, making it particularly dangerous as it can disrupt email services across an entire organization. The flaw manifests when the system encounters TNEF-encoded messages containing crafted rich text bodies that trigger improper handling during the conversion process to plain text format. This particular vulnerability demonstrates the complexity of email security systems where the interaction between different message formats and content processing can create unexpected failure points. The issue is categorized under CWE-129 Input Validation, indicating that inadequate validation of input parameters leads to system instability.
The technical exploitation of this vulnerability occurs through the manipulation of TNEF (Transport Neutral Encapsulation Format) messages which are commonly used in microsoft exchange environments to preserve rich text formatting during email transmission. When Sophos PureMessage processes these messages, the crafted rich text body content causes the system to fail during the plain text conversion phase, ultimately leading to the termination of the EdgeTransport.exe process. This process termination represents a complete denial of service condition as the email transport service becomes unavailable, preventing legitimate email traffic from being processed. The vulnerability's relationship to CVE-2008-7104 suggests a pattern of similar flaws in the same software component, indicating a broader architectural issue with how the system handles certain types of rich text content. From an attack perspective, this vulnerability requires minimal privileges and can be exploited remotely, making it particularly attractive to threat actors seeking to disrupt email services. The ATT&CK framework would categorize this as a Denial of Service attack using system resource exhaustion or process termination techniques.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise business continuity and email security posture. Organizations relying on Sophos PureMessage for their email filtering and security operations would experience complete email service outages until the affected system is patched or restarted. The vulnerability affects the core email transport functionality, meaning that legitimate business communications could be severely impacted during the attack window. Network administrators would face challenges in identifying the root cause of email service failures, as the termination of EdgeTransport.exe would appear as an unexpected system crash rather than a targeted attack. The vulnerability's presence in versions prior to 3.0.2 indicates that this was a known issue that required immediate remediation, and organizations would need to implement proper patch management procedures to avoid exploitation. The flaw demonstrates the importance of robust input validation in security appliances and highlights how seemingly benign message format handling can create critical system instability.
Mitigation strategies for this vulnerability involve immediate patching to version 3.0.2 or later, which would address the improper handling of TNEF-encoded messages during text conversion. Organizations should also implement additional monitoring of EdgeTransport.exe process stability and establish alerting mechanisms for unexpected process terminations. Network segmentation and email security policies should be reviewed to limit the potential impact of such attacks, while redundant email security solutions can provide fallback protection. Security teams should also consider implementing message filtering rules that can detect and quarantine suspicious TNEF content before it reaches the vulnerable processing components. The incident underscores the necessity of thorough regression testing for security updates and proper validation of message handling components in email security solutions. Organizations should also maintain detailed incident response procedures for dealing with service disruptions and ensure that backup email processing capabilities are available to maintain business continuity during remediation activities.