CVE-2021-38490 in MobileTogether Server
Summary
by MITRE • 08/11/2021
Altova MobileTogether Server before 7.3 SP1 allows XML exponential entity expansion, a different vulnerability than CVE-2021-37425.
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Analysis
by VulDB Data Team • 08/16/2021
The vulnerability identified as CVE-2021-38490 affects Altova MobileTogether Server versions prior to 7.3 Service Pack 1 and represents a distinct form of XML external entity processing vulnerability that specifically targets the exponential entity expansion pattern. This weakness enables attackers to exploit the server's XML parser through carefully crafted malicious XML documents that contain recursively nested entity declarations, leading to resource exhaustion and potential denial of service conditions. The vulnerability operates independently from CVE-2021-37425, which indicates that while both issues involve XML processing, they manifest through different attack vectors and implementation flaws within the server's XML handling mechanisms. The exponential entity expansion vulnerability falls under the category of CWE-400, specifically addressing unchecked resource consumption through XML external entity expansion, which is a well-documented pattern in XML security vulnerabilities. This type of vulnerability is particularly dangerous because it can cause servers to consume excessive memory and processing resources when attempting to resolve deeply nested entity references, potentially leading to complete system unavailability.
The technical exploitation of this vulnerability requires an attacker to craft XML documents containing entities that reference other entities in a recursive manner, creating an exponential growth in the number of entity expansions that must be processed. When the MobileTogether Server attempts to parse such documents, the XML parser begins resolving these entities, and each expansion can trigger additional entity resolutions, leading to a rapid consumption of system resources. The server's XML processing capabilities are designed to handle standard XML documents, but the exponential nature of entity expansion means that even relatively small malicious documents can cause significant resource consumption. This type of attack is classified under the ATT&CK technique T1499.004, which describes resource exhaustion attacks targeting XML parsers and processing systems. The vulnerability specifically impacts the server's ability to process incoming XML data through its MobileTogether Server functionality, where users may upload or submit XML content that gets parsed by the server's underlying XML processing libraries.
The operational impact of CVE-2021-38490 can be severe for organizations relying on Altova MobileTogether Server for their mobile application development and deployment workflows. A successful exploitation can lead to complete denial of service conditions where legitimate users cannot access server functionality due to resource exhaustion, potentially disrupting business operations and application development cycles. The vulnerability affects the server's availability and stability, as the exponential entity expansion can cause memory leaks, process crashes, and system slowdowns that may require manual intervention to resolve. Organizations using MobileTogether Server for enterprise mobile application development, testing, or deployment may face significant operational disruptions if this vulnerability is exploited in production environments. The impact extends beyond simple availability issues to potentially affecting data integrity and system reliability, as the server may become unresponsive to legitimate requests while processing malicious XML content. This vulnerability represents a critical risk for organizations that process untrusted XML input through the MobileTogether Server platform, particularly in environments where the server handles user-submitted content or integrates with external systems that provide XML data.
Mitigation strategies for CVE-2021-38490 primarily involve applying the vendor-provided patch or upgrade to Altova MobileTogether Server version 7.3 Service Pack 1, which includes fixes specifically addressing the exponential entity expansion vulnerability. Organizations should also implement XML input validation and sanitization measures to prevent malicious XML content from reaching the server's XML parser, including configuring appropriate limits on entity expansion depth and size. Network-level protections such as web application firewalls can help detect and block suspicious XML content patterns before they reach the server. Additionally, organizations should implement monitoring and alerting systems to detect unusual resource consumption patterns that may indicate exploitation attempts. The implementation of XML security configurations that disable external entity processing or limit the number of entity expansions allowed per document can provide additional defense-in-depth measures. Security teams should also conduct regular vulnerability assessments and penetration testing to identify potential attack vectors and ensure that all XML processing components are properly configured to prevent similar vulnerabilities. Organizations should consider implementing automated patch management processes to ensure timely application of security updates and maintain awareness of similar vulnerabilities in other XML processing components within their infrastructure.