CVE-2017-3208 in Flamingo amf-serializer
Summary
by MITRE
The Java implementation of AMF3 deserializers used by Flamingo amf-serializer by Exadel, version 2.2.0, allows external entity references (XXEs) from XML documents embedded within AMF3 messages. If the XML parsing is handled incorrectly it could potentially expose sensitive data on the server, denial of service, or server side request forgery.
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Analysis
by VulDB Data Team • 12/26/2024
The vulnerability identified as CVE-2017-3208 represents a critical security flaw within the Java implementation of AMF3 deserializers used by Flamingo amf-serializer version 2.2.0 developed by Exadel. This issue specifically targets the processing of XML documents that are embedded within AMF3 messages, creating a pathway for malicious actors to exploit external entity references through XML parsing mechanisms. The vulnerability stems from inadequate input validation and secure XML processing practices within the deserialization framework, allowing attackers to manipulate XML content that is subsequently parsed by the application.
The technical flaw manifests when the AMF3 deserializer processes XML data embedded within serialized messages without proper sanitization or secure parsing configurations. This weakness enables attackers to craft malicious AMF3 messages containing specially crafted XML content that triggers XML external entity (XXE) processing. When the application attempts to deserialize these messages, the embedded XML is parsed without appropriate restrictions, potentially allowing the exploitation of XML parsing vulnerabilities that can lead to information disclosure, denial of service conditions, or server-side request forgery attacks. The vulnerability is particularly concerning because it operates at the deserialization layer, where untrusted data from external sources is processed and interpreted by the application.
From an operational impact perspective, this vulnerability presents significant risks to systems utilizing the Flamingo amf-serializer library. Attackers could potentially extract sensitive data from the server by referencing external entities that contain internal system information, file contents, or database credentials. The denial of service aspect of this vulnerability could disrupt service availability by causing the application to consume excessive resources during XML parsing operations or by triggering infinite loops in malformed XML processing. Additionally, the server-side request forgery component allows attackers to make unauthorized requests from the vulnerable server, potentially enabling them to access internal services or bypass security controls that would normally protect against external threats.
The security implications of CVE-2017-3208 align with common weaknesses documented in the CWE (Common Weakness Enumeration) catalog, specifically CWE-611, which addresses Improper Restriction of XML External Entity Reference, and CWE-400, which covers Uncontrolled Resource Consumption. This vulnerability also maps to several ATT&CK (Attack Tree for Threats and Countermeasures) techniques including T1059 for command and scripting interpreter and T1190 for exploit public-facing application, as attackers can leverage this flaw to execute arbitrary code or gain unauthorized access to system resources. The attack surface is particularly broad given that AMF3 deserialization is commonly used in enterprise applications and web services that handle serialized data from multiple sources.
Mitigation strategies for this vulnerability should focus on implementing secure XML parsing practices and restricting external entity processing within the AMF3 deserializer. Organizations should immediately upgrade to patched versions of the Flamingo amf-serializer library or implement proper input validation and sanitization measures that prevent malicious XML content from being processed. Security configurations should disable external entity resolution and DTD processing during XML parsing operations. Additionally, network-level controls such as firewalls and intrusion detection systems should be configured to monitor for suspicious AMF3 message patterns and potential exploitation attempts. Regular security assessments and code reviews should be conducted to identify similar vulnerabilities in other deserialization components throughout the application stack, ensuring comprehensive protection against similar XXE attack vectors that could compromise system integrity and data confidentiality.