CVE-2017-5641 in vCenter Server
Summary
by MITRE
Previous versions of Apache Flex BlazeDS (4.7.2 and earlier) did not restrict which types were allowed for AMF(X) object deserialization by default. During the deserialization process code is executed that for several known types has undesired side-effects. Other, unknown types may also exhibit such behaviors. One vector in the Java standard library exists that allows an attacker to trigger possibly further exploitable Java deserialization of untrusted data. Other known vectors in third party libraries can be used to trigger remote code execution.
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Analysis
by VulDB Data Team • 12/26/2024
The vulnerability identified as CVE-2017-5641 affects Apache Flex BlazeDS versions 4.7.2 and earlier, representing a critical security flaw in the Action Message Format eXtended (AMFX) deserialization mechanism. This issue stems from insufficient type restrictions during the object deserialization process, creating an attack surface that allows malicious actors to exploit the system through crafted AMF(X) data packets. The flaw specifically targets the default configuration of BlazeDS which fails to validate or restrict the types of objects that can be deserialized, thereby permitting arbitrary code execution through the deserialization chain.
The technical implementation of this vulnerability operates through the Java deserialization process where untrusted data is converted into executable objects. When BlazeDS processes AMF(X) messages, it attempts to deserialize objects without proper type validation, enabling attackers to inject malicious objects that trigger unintended behavior during deserialization. The vulnerability leverages the Java standard library's deserialization capabilities, specifically targeting a known vector that allows attackers to initiate further exploitable Java deserialization of untrusted data. This mechanism creates a chain reaction where the initial deserialization triggers additional code execution that can lead to complete system compromise.
The operational impact of CVE-2017-5641 extends beyond simple code execution, as it represents a severe remote code execution vulnerability that can be exploited without authentication. Attackers can craft malicious AMF(X) messages that, when processed by the vulnerable BlazeDS server, trigger arbitrary code execution on the target system. This vulnerability aligns with CWE-502 which describes "Deserialization of Untrusted Data" as a critical weakness in software security, where the deserialization process can be manipulated to execute malicious code. The risk is compounded by the fact that multiple known vectors exist in third-party libraries that can be leveraged to achieve remote code execution, making this vulnerability particularly dangerous in enterprise environments where such libraries are commonly used.
Security professionals should recognize this vulnerability as a prime example of how insufficient input validation during deserialization can lead to complete system compromise, particularly in applications that handle untrusted data from external sources. The attack surface is broadened by the presence of known attack vectors in the Java standard library and third-party components, creating multiple paths for exploitation. Organizations using Apache Flex BlazeDS should immediately implement mitigations including updating to patched versions, implementing strict type filtering during deserialization, and applying network-level restrictions to prevent unauthorized access to BlazeDS endpoints. This vulnerability demonstrates the critical importance of secure deserialization practices and aligns with ATT&CK technique T1059.007 which covers "Command and Scripting Interpreter: PowerShell" in the context of remote code execution through deserialization vulnerabilities. The remediation strategy should also include implementing proper application-level firewalls, network segmentation, and regular security assessments to prevent similar vulnerabilities from being introduced into the system architecture.