CVE-2016-3720 in Data Format Extension
Summary
by MITRE
XML external entity (XXE) vulnerability in XmlMapper in the Data format extension for Jackson (aka jackson-dataformat-xml) allows attackers to have unspecified impact via unknown vectors.
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Analysis
by VulDB Data Team • 08/26/2024
The CVE-2016-3720 vulnerability represents a critical XML external entity processing flaw within the Jackson data format extension for XML parsing. This vulnerability specifically affects the XmlMapper component of the Jackson library, which is widely used for processing XML data in Java applications. The vulnerability stems from insufficient validation of external entity references during XML document parsing, creating a potential attack surface that could be exploited by malicious actors to manipulate XML processing behavior. The affected component is part of the broader Jackson ecosystem that provides serialization and deserialization capabilities for various data formats including XML, JSON, and binary formats. When applications process untrusted XML input through XmlMapper without proper safeguards, they become susceptible to this vulnerability. The unspecified impact vector indicates that attackers could potentially leverage this flaw in multiple ways depending on the specific application context and environment configuration. This vulnerability is particularly concerning because Jackson is a foundational library used across numerous enterprise applications, web services, and middleware components, making the potential attack surface extensive and widespread. The vulnerability exists at the core parsing layer where XML documents are interpreted and converted into application objects, creating a fundamental security risk that affects the integrity and confidentiality of data processing operations.
The technical flaw manifests when the XmlMapper processes XML documents containing external entity declarations that reference external resources. Attackers can craft malicious XML payloads that include external entity references pointing to internal network resources, external servers, or even local files on the processing system. The vulnerability occurs because the XML parser does not properly restrict or validate external entity resolution, allowing arbitrary XML entities to be resolved and processed. This behavior aligns with CWE-611, which classifies the weakness as improper restriction of XML external entity reference, and specifically relates to the broader category of XML external entity processing vulnerabilities. The flaw can be exploited through various attack vectors including file inclusion attacks, server-side request forgery, and information disclosure scenarios. When external entities are resolved, they can trigger network connections to internal systems, cause denial of service through resource exhaustion, or enable attackers to read sensitive files from the server filesystem. The vulnerability is particularly dangerous because it can be triggered through legitimate XML parsing operations, making it difficult to detect and prevent through traditional network monitoring approaches.
The operational impact of CVE-2016-3720 extends beyond simple data corruption or information disclosure, as it can lead to complete system compromise when exploited in conjunction with other vulnerabilities or attack techniques. Applications using the affected Jackson XmlMapper component could experience unauthorized data access, system resource exhaustion, or even remote code execution depending on the specific environment and configuration. The vulnerability can be particularly devastating in cloud environments or containerized applications where XML processing is common and the attack surface is extensive. Attackers can leverage this vulnerability to perform reconnaissance activities by accessing internal network resources that would normally be protected by firewalls or network segmentation. The impact is further amplified when applications process XML data from untrusted sources such as user input, third-party APIs, or file uploads, as these scenarios provide natural attack vectors for exploitation. Organizations using Jackson-based applications in production environments face significant risk of data breaches, service disruption, and compliance violations if this vulnerability remains unpatched. The vulnerability also affects the integrity of application processing workflows, as malicious XML content can cause unexpected behavior in applications that rely on XML data for business logic processing.
Mitigation strategies for CVE-2016-3720 should focus on both immediate patching and defensive configuration measures. The primary remediation involves upgrading to Jackson versions that include proper XML external entity validation and restriction mechanisms. Organizations should also implement XML parser configurations that disable external entity resolution entirely or restrict it to known safe sources. Security measures should include input validation and sanitization of XML data, particularly when processing untrusted content from external sources. The implementation of web application firewalls and XML parsing security controls can provide additional layers of protection against exploitation attempts. Organizations should also conduct comprehensive vulnerability assessments to identify all applications using affected Jackson versions and ensure proper patch management procedures are in place. The ATT&CK framework categorizes this vulnerability under the T1213 technique for Data from Information Repositories, as attackers can extract sensitive information through external entity resolution. Regular security testing including XML injection vulnerability assessments should be implemented as part of the overall security posture to prevent exploitation of similar vulnerabilities in the future. Network segmentation and access controls should be strengthened to limit the potential impact of successful exploitation attempts. Proper logging and monitoring of XML processing activities can help detect anomalous behavior that may indicate exploitation attempts. The vulnerability also underscores the importance of maintaining up-to-date security libraries and implementing automated vulnerability scanning processes to identify and remediate similar issues before they can be exploited in production environments.