CVE-2002-1020 in Content Server
Summary
by MITRE
The library feature for Adobe Content Server 3.0 allows a remote attacker to check out an eBook even when the maximum number of loans is exceeded by accessing the "Add to bookbag" feature when the server reports that no more copies are available.
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Analysis
by VulDB Data Team • 04/18/2019
This vulnerability exists in Adobe Content Server 3.0's library feature implementation where the system fails to properly enforce loan limits during the checkout process. The flaw occurs when users attempt to add titles to their bookbag through the web interface after the server has already indicated that no copies are available for checkout. This represents a classic access control bypass vulnerability that undermines the digital rights management system's integrity. The issue stems from improper state validation within the server's checkout workflow where the system does not re-evaluate available copy counts between the initial availability check and the actual checkout operation.
The technical implementation flaw lies in the server's failure to maintain consistent state management throughout the checkout process. When the system reports "no more copies available" to the user interface, it should immediately prevent any further checkout attempts regardless of subsequent user actions. However, Adobe Content Server 3.0 allows users to proceed with adding titles to their bookbag even after receiving the unavailable status message, effectively circumventing the intended copy limitation mechanism. This behavior violates fundamental principles of secure access control and demonstrates poor input validation within the application's business logic layer.
The operational impact of this vulnerability extends beyond simple unauthorized access to digital content. It enables attackers to consume more licenses than permitted, potentially leading to revenue loss for content providers and undermining the entire digital rights management ecosystem. This type of vulnerability can be exploited by malicious users to gain unlimited access to premium content, particularly affecting publishers and content distributors who rely on strict licensing controls. The flaw could be amplified through automated tools that repeatedly attempt checkout operations, creating a denial of service condition for legitimate users while simultaneously violating licensing agreements.
From a cybersecurity perspective, this vulnerability maps to CWE-665 Improper Initialization and CWE-347 Improper Verification of Cryptographic Signature, as it represents a failure in proper state validation and access control verification. The attack vector aligns with ATT&CK technique T1078 Valid Accounts, where an attacker exploits legitimate system functionality to bypass restrictions. The vulnerability also demonstrates characteristics of T1566 Phishing, as attackers could potentially use this flaw to create deceptive scenarios where users believe they are restricted from accessing content when they are actually able to circumvent those restrictions. Organizations should implement immediate mitigations including patching to the latest Adobe Content Server versions, implementing additional access logging, and monitoring for unusual checkout patterns that might indicate exploitation attempts.