CVE-2020-25649: Fasterxml Jackson-databind XXE Vulnerability

CVE-2020-25649 Overview

A flaw was found in FasterXML Jackson Databind, where it did not have entity expansion secured properly. This flaw allows vulnerability to XML external entity (XXE) attacks. The highest threat from this vulnerability is data integrity, as attackers can potentially modify data through malicious XML entity injection. Jackson Databind is a widely used Java library for JSON processing, making this vulnerability particularly impactful across numerous enterprise applications and frameworks.

Critical Impact

This XXE vulnerability in Jackson Databind allows attackers to exploit improper XML entity expansion, potentially compromising data integrity across numerous Oracle, NetApp, Apache, and other enterprise products that rely on this core library.

Affected Products

• FasterXML Jackson-databind
• NetApp OnCommand API Services, Workflow Automation, and Service Level Manager
• Fedora 32
• Quarkus
• Apache IoTDB
• Oracle Agile PLM, Banking APIs, Banking Platform, Commerce Platform, Coherence
• Oracle Communications (multiple products including Billing and Revenue Management, Messaging Server)
• Oracle Primavera Gateway, WebCenter Portal, Utilities Framework
• Oracle Retail XStore Point of Service

Discovery Timeline

• December 3, 2020 - CVE-2020-25649 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-25649

Vulnerability Analysis

This vulnerability arises from improper handling of XML external entity (XXE) expansion within the Jackson Databind library. When processing XML input, the library fails to properly restrict or disable external entity references, allowing attackers to inject malicious XML content that can reference external resources or local files.

The attack requires no authentication and can be executed remotely over the network. While the vulnerability does not directly enable confidentiality breaches or denial of service, it poses a significant risk to data integrity. An attacker can leverage this flaw to manipulate application data through carefully crafted XML payloads containing external entity declarations.

The widespread adoption of Jackson Databind across Java-based enterprise applications amplifies the impact significantly. Multiple Oracle products, Apache frameworks (Kafka, Hive, Zookeeper, Flink), and other enterprise solutions incorporate this library, creating a broad attack surface.

Root Cause

The root cause of CVE-2020-25649 lies in insufficient security controls around XML entity expansion within the Jackson Databind XML processing components. The library did not implement proper restrictions on external entity references (CWE-611), allowing XML parsers to resolve and include external resources during document processing.

Specifically, the XML parsing configuration failed to disable features such as external general entities, external parameter entities, and external DTD references. This configuration oversight allows attackers to craft XML documents that, when processed, can trigger unintended external resource loading or data manipulation.

Attack Vector

The attack vector for this vulnerability is network-based and requires no user interaction or special privileges. An attacker can exploit this vulnerability by sending a specially crafted XML payload to an application that processes XML using a vulnerable version of Jackson Databind.

The attack typically involves:

1. Identifying an endpoint that accepts XML input and uses Jackson Databind for processing
2. Crafting a malicious XML document containing external entity declarations
3. Submitting the payload to trigger the XXE processing
4. Exploiting the entity expansion to manipulate data or access internal resources

When exploiting XXE vulnerabilities, attackers commonly define external entities that reference local files or internal network resources. The XML parser then attempts to resolve these references, potentially exposing sensitive information or allowing data manipulation.

Detection Methods for CVE-2020-25649

Indicators of Compromise

• Unusual XML payloads in application logs containing <!DOCTYPE> declarations with external entity references
• Unexpected outbound connections from application servers to external hosts during XML processing
• Log entries indicating XML parsing errors related to entity resolution or DTD loading
• Application behavior anomalies when processing XML input, such as unexpected file access attempts

Detection Strategies

• Monitor application logs for XML parsing activities that reference external entities or DTDs
• Implement Web Application Firewall (WAF) rules to detect and block XML payloads containing suspicious entity declarations
• Use software composition analysis (SCA) tools to identify Jackson Databind library versions in your environment
• Review network traffic for unexpected outbound connections initiated during XML processing operations

Monitoring Recommendations

• Enable verbose logging for XML processing components to capture entity resolution attempts
• Configure intrusion detection systems to alert on XXE attack patterns in HTTP request bodies
• Implement application-level monitoring to track XML parsing exceptions and failures
• Establish baseline metrics for XML processing behavior to detect anomalous patterns

How to Mitigate CVE-2020-25649

Immediate Actions Required

• Inventory all applications using FasterXML Jackson Databind and identify vulnerable versions
• Prioritize patching for internet-facing applications and those processing untrusted XML input
• Implement input validation and sanitization for XML data at application boundaries
• Configure XML parsers to disable external entity processing where possible

Patch Information

FasterXML has addressed this vulnerability in patched versions of Jackson Databind. Organizations should upgrade to the latest secure version of the library. Detailed information about the fix is available in GitHub Issue #2589.

For Oracle products, patches are available through multiple Critical Patch Updates (CPUs). Consult the Oracle April 2021 CPU, Oracle July 2021 CPU, Oracle October 2021 CPU, Oracle January 2022 CPU, and subsequent security advisories for product-specific patches.

NetApp has also released guidance through their Security Advisory ntap-20210108-0007.

Workarounds

• Disable external entity processing in XML parser configurations by setting appropriate features (e.g., XMLConstants.FEATURE_SECURE_PROCESSING)
• Implement strict input validation to reject XML documents containing DOCTYPE declarations or entity references
• Use application-level firewalls to filter incoming XML content for XXE attack patterns
• Consider using alternative serialization formats like JSON where XML processing is not strictly required

# Maven dependency update example for Jackson Databind
# Update pom.xml to use patched version
mvn versions:use-latest-releases -Dincludes=com.fasterxml.jackson.core:jackson-databind

# Verify the updated dependency version
mvn dependency:tree | grep jackson-databind