CVE-2008-7104 in PureMessage for Microsoft Exchange
Summary
by MITRE
Sophos PureMessage Scanner service (PMScanner.exe) in PureMessage for Microsoft Exchange 3.0 before 3.0.2 allows remote attackers to cause a denial of service (message queue delay and incomplete spam rule update) via a crafted (1) RTF or (2) PDF file.
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Analysis
by VulDB Data Team • 08/20/2021
The vulnerability identified as CVE-2008-7104 affects Sophos PureMessage Scanner service (PMScanner.exe) in PureMessage for Microsoft Exchange versions 3.0 and earlier, specifically before version 3.0.2. This flaw represents a significant security concern within enterprise email security solutions where the scanner service becomes vulnerable to remote exploitation. The vulnerability stems from inadequate input validation and processing of specially crafted email attachments, particularly those formatted as rich text format or portable document format files. The attack vector enables remote adversaries to craft malicious email content that triggers specific processing behaviors within the scanner service, leading to system instability and operational degradation.
The technical implementation of this vulnerability occurs when the PMScanner.exe service attempts to process maliciously crafted RTF or PDF attachments. The service lacks proper sanitization and boundary checking mechanisms for these file formats, allowing attackers to construct payloads that cause the scanner to enter an infinite processing loop or consume excessive system resources. When such malformed attachments are received by the email server, the PureMessage scanner service begins processing them but encounters unexpected data structures that it cannot properly handle. This results in the service becoming unresponsive or significantly delayed in processing subsequent messages, creating a cascading effect that impacts the entire email queue management system.
The operational impact of this vulnerability manifests as both message queue delays and incomplete spam rule updates within the email security infrastructure. When the scanner service becomes compromised, legitimate email messages begin to queue up in the system as the service struggles to process the malicious attachments. This creates a backlog of messages that cannot be properly scanned or delivered, effectively causing a denial of service condition for the email system. Additionally, the incomplete spam rule updates occur because the scanner service cannot properly refresh its rule databases while processing the malformed content, leading to potential security gaps where malicious content might bypass detection mechanisms. The vulnerability essentially creates a scenario where the security solution becomes a liability rather than a protective measure.
This vulnerability aligns with CWE-129 Input Validation and OWASP Top Ten category A03: Injection, as it represents an input validation failure that allows attackers to manipulate the system's processing behavior through crafted inputs. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 Network Denial of Service and T1078 Valid Accounts, as it enables attackers to disrupt service availability and potentially leverage compromised scanner services for further malicious activities. Organizations should implement immediate mitigations including updating to PureMessage version 3.0.2 or later, implementing additional email filtering rules to block suspicious RTF and PDF attachments, and establishing monitoring procedures to detect unusual scanner service behavior. Network segmentation and rate limiting on email processing can also help reduce the impact of such attacks, while regular security assessments should verify that similar vulnerabilities do not exist in other components of the email security infrastructure.