CVE-2004-0796 in SpamAssassin
Summary
by MITRE
SpamAssassin 2.5x, and 2.6x before 2.64, allows remote attackers to cause a denial of service via certain malformed messages.
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Analysis
by VulDB Data Team • 06/02/2019
The vulnerability identified as CVE-2004-0796 affects SpamAssassin versions 2.5x and 2.6x prior to 2.64, presenting a significant denial of service risk that can be exploited by remote attackers through the manipulation of message formatting. This issue stems from inadequate input validation mechanisms within the spam filtering software, which fails to properly handle malformed email content that could trigger unexpected behavior in the processing pipeline. The flaw specifically manifests when SpamAssassin encounters certain types of malformed messages that cause the application to consume excessive system resources or enter unstable states, ultimately leading to service disruption for legitimate users.
The technical root cause of this vulnerability lies in the insufficient sanitization and validation of email message structures within SpamAssassin's processing framework. When processing incoming messages that contain malformed headers, body content, or encoding sequences, the software does not adequately protect against malformed data that could cause memory allocation issues or processing loops. This weakness enables attackers to craft specific email payloads that, when processed by the vulnerable SpamAssassin instances, trigger resource exhaustion or application instability. The vulnerability operates at the application layer and can be exploited without requiring authentication, making it particularly dangerous in environments where spam filtering services are exposed to untrusted network traffic.
From an operational perspective, this vulnerability creates substantial risk for organizations relying on SpamAssassin for email security. The denial of service condition can result in complete disruption of email services, as the spam filtering system becomes unresponsive or crashes entirely. This impacts not only the spam filtering capabilities but can also affect the overall email infrastructure, potentially causing cascading failures in email delivery and system availability. The attack surface is broad since email systems typically process messages from untrusted sources, and the vulnerability can be exploited through simple email transmission without requiring special privileges or credentials. Organizations may experience significant downtime and service degradation while attempting to restore normal operations after exploitation.
The vulnerability aligns with CWE-400, which addresses "Uncontrolled Resource Consumption," and represents a classic example of a resource exhaustion attack that can be executed remotely. From an ATT&CK framework perspective, this vulnerability maps to techniques involving denial of service operations and can be categorized under T1499.004 for "Network Denial of Service" and potentially T1566 for "Phishing" if attackers leverage the service disruption for additional malicious activities. The impact extends beyond simple availability concerns as it can be used as a stepping stone for more sophisticated attacks or as part of broader campaign strategies to disable email security controls. Organizations should implement immediate patching strategies and consider network segmentation to limit the exposure of vulnerable SpamAssassin instances to untrusted traffic sources.
Mitigation strategies should prioritize the immediate upgrade of SpamAssassin installations to version 2.64 or later, which contains the necessary fixes for this vulnerability. System administrators should also implement additional monitoring and alerting mechanisms to detect unusual resource consumption patterns that might indicate exploitation attempts. Network-level protections such as rate limiting and email content filtering can provide additional defense in depth. Organizations should also consider implementing redundant spam filtering solutions and establishing incident response procedures specifically addressing denial of service scenarios. Regular security assessments and vulnerability scanning should include verification of SpamAssassin versions and configuration settings to ensure that the system remains protected against similar vulnerabilities. The remediation process should include thorough testing of updated configurations to prevent unintended service disruptions while maintaining effective spam filtering capabilities.