CVE-2005-1266 in SpamAssassin
Summary
by MITRE
Apache SpamAssassin 3.0.1, 3.0.2, and 3.0.3 allows remote attackers to cause a denial of service (CPU consumption and slowdown) via a message with a long Content-Type header without any boundaries.
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Analysis
by VulDB Data Team • 07/04/2025
Apache SpamAssassin versions 3.0.1 through 3.0.3 contain a critical vulnerability that enables remote attackers to execute denial of service attacks by crafting malicious email messages with excessively long Content-Type headers lacking boundary specifications. This vulnerability resides in the spam filtering engine's processing logic for email headers, specifically affecting how the system handles malformed Content-Type declarations. The flaw manifests when SpamAssassin attempts to parse and analyze email messages containing Content-Type headers that exceed normal length parameters while simultaneously lacking proper boundary delimiters that typically define multipart message structures. The absence of boundary specifications forces the spam filtering system into inefficient parsing routines that consume excessive cpu cycles and memory resources during message evaluation. This behavior creates a resource exhaustion condition that can severely impact system performance and availability, effectively rendering the spam filtering service ineffective for legitimate email traffic.
The technical implementation of this vulnerability aligns with CWE-400, which addresses unchecked resource consumption, and represents a classic example of a denial of service attack through resource exhaustion. The attack vector operates at the application layer, specifically targeting the message processing components of SpamAssassin's core filtering engine. When the system encounters a message with an extended Content-Type header devoid of boundary information, it enters into iterative processing loops that continue until system resources are depleted. This processing pattern creates a computationally expensive operation that can be exploited by attackers to consume system resources at an exponential rate, effectively overwhelming the spam filtering service. The vulnerability demonstrates poor input validation and insufficient boundary checking within the email header parsing routines, allowing malformed input to trigger inefficient processing paths that do not properly account for edge cases in header formatting.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on SpamAssassin for email security and filtering. The attack can be executed with minimal technical expertise, requiring only the ability to send specially crafted email messages to the target system. The impact extends beyond simple service disruption, as the resource consumption patterns can affect overall system stability and potentially impact other services running on the same infrastructure. Organizations may experience degraded performance, increased latency in email processing, and potential complete service outages during sustained attack periods. The vulnerability affects the availability aspect of the security triad by compromising the system's ability to process legitimate email messages, creating a scenario where the very security tool designed to protect against spam becomes a target for disruption. Network administrators and security teams must recognize that this attack can be executed from external sources without requiring authentication or privileged access, making it particularly dangerous in environments with public email gateways or shared infrastructure.
The mitigation strategies for this vulnerability should include immediate patching to versions 3.0.4 and later, which contain the necessary fixes to properly handle malformed Content-Type headers and implement proper boundary validation. Organizations should also implement rate limiting and resource monitoring to detect unusual processing patterns that may indicate exploitation attempts. Network-level protections such as email filtering at the perimeter can help reduce the volume of potentially malicious messages reaching the SpamAssassin system. Additionally, implementing proper input validation and boundary checking within the email parsing components provides defense in depth against similar vulnerabilities. The remediation process should also include monitoring for abnormal CPU utilization patterns and implementing automated alerts when processing times exceed normal thresholds. Security teams should conduct regular vulnerability assessments to identify similar parsing weaknesses in other email processing systems and ensure that input validation mechanisms are robust enough to handle malformed data without causing system resource exhaustion. The vulnerability serves as a reminder of the importance of proper input validation and resource management in security applications to prevent attackers from exploiting parsing logic for denial of service purposes.