CVE-2006-0052 in Mailman
Summary
by MITRE
The attachment scrubber (Scrubber.py) in Mailman 2.1.5 and earlier, when using Python s library email module 2.5, allows remote attackers to cause a denial of service (mailing list delivery failure) via a multipart MIME message with a single part that has two blank lines between the first boundary and the end boundary.
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Analysis
by VulDB Data Team • 06/23/2025
The vulnerability described in CVE-2006-0052 represents a critical denial of service flaw within the Mailman mailing list management system, specifically affecting versions 2.1.5 and earlier. This issue manifests in the attachment scrubber component known as Scrubber.py, which serves as a crucial filter for processing incoming email messages before they are distributed to mailing list subscribers. The vulnerability exploits a fundamental parsing inconsistency within the Python email module version 2.5, creating a scenario where legitimate email traffic can be disrupted through carefully crafted malicious messages. The flaw occurs when the system encounters multipart MIME messages that contain a single part but include an unusual formatting pattern with two blank lines positioned between the first boundary delimiter and the final boundary delimiter.
The technical implementation of this vulnerability stems from the improper handling of MIME boundary parsing within the email processing pipeline. When Mailman's Scrubber.py component processes a multipart message that contains exactly one part but has two blank lines between the initial boundary and the terminating boundary, the Python email module's parser becomes confused during the boundary detection algorithm. This parsing failure causes the system to either fail to properly identify the message boundaries or to misinterpret the message structure entirely, resulting in the complete breakdown of the email processing routine. The flaw is particularly insidious because it requires no authentication or special privileges from the attacker, making it accessible to anyone capable of sending email to the affected mailing list. The vulnerability directly relates to CWE-129, which addresses improper handling of length parameters, and CWE-131, concerning improper handling of buffer boundaries, as the parsing error essentially creates a boundary condition that causes the system to process data incorrectly.
The operational impact of this vulnerability extends beyond simple service disruption, as it can effectively瘫痪 entire mailing list operations and potentially compromise the reliability of critical communication channels. When this vulnerability is exploited, the affected Mailman server experiences complete failure in processing incoming messages, leading to a cascading effect where legitimate emails are not delivered to subscribers, and the mailing list effectively becomes non-functional. This denial of service condition can persist until the system is manually restarted or the problematic message is manually removed from the processing queue. Organizations relying on Mailman for critical communications, including those in government, healthcare, or financial sectors, face significant operational risks when this vulnerability exists in their infrastructure. The attack vector is particularly concerning from an adversarial perspective as it can be executed through simple email transmission without requiring sophisticated tools or deep system knowledge, making it a preferred method for disrupting mailing list services.
Mitigation strategies for this vulnerability should focus on immediate version upgrades to Mailman 2.1.6 or later, which contain patches specifically addressing the MIME boundary parsing issue. System administrators should also implement additional email filtering mechanisms that can detect and quarantine suspicious multipart messages before they reach the vulnerable Scrubber.py component. Network-level protections such as rate limiting and message size restrictions can help reduce the impact of potential attacks, while monitoring systems should be configured to detect unusual patterns in mailing list processing failures. From a security hardening perspective, implementing proper input validation and boundary checking within the email processing pipeline can prevent similar issues from occurring in other components. The vulnerability also highlights the importance of maintaining up-to-date third-party libraries and regularly reviewing security advisories for all components within the email processing stack. This incident aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and demonstrates how seemingly minor parsing inconsistencies in standard library components can create significant security vulnerabilities in enterprise email systems. Organizations should establish robust patch management procedures to ensure timely deployment of security updates and maintain comprehensive incident response plans to address service disruptions caused by such vulnerabilities.