CVE-2016-5229 in Bamboo
Summary
by MITRE
Atlassian Bamboo before 5.11.4.1 and 5.12.x before 5.12.3.1 does not properly restrict permitted deserialized classes, which allows remote attackers to execute arbitrary code via vectors related to XStream Serialization.
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Analysis
by VulDB Data Team • 09/09/2022
The vulnerability identified as CVE-2016-5229 represents a critical deserialization flaw in Atlassian Bamboo versions prior to 5.11.4.1 and 5.12.x versions prior to 5.12.3.1. This issue stems from insufficient restrictions on permitted deserialized classes within the XStream serialization framework, creating a pathway for remote code execution attacks. The vulnerability falls under the category of insecure deserialization, which is classified as CWE-502 in the Common Weakness Enumeration catalog and maps to attack techniques in the MITRE ATT&CK framework under T1203 and T1059. The flaw specifically manifests when Bamboo processes serialized data from untrusted sources without proper validation of the types being deserialized.
The technical implementation of this vulnerability exploits the XStream library's default behavior of allowing deserialization of arbitrary Java classes. When an attacker can inject malicious serialized data into Bamboo's processing pipeline, the system will attempt to deserialize this data without adequate class filtering. This creates an opportunity for attackers to leverage pre-existing Java classes that can be used to execute arbitrary commands on the target system. The vulnerability is particularly dangerous because it allows for remote code execution without requiring authentication, making it an attractive target for automated exploitation. The XStream library's default configuration permits deserialization of classes from the Java standard library and other common libraries, which can be leveraged to construct malicious payloads.
The operational impact of CVE-2016-5229 extends beyond simple remote code execution to encompass complete system compromise. Attackers can leverage this vulnerability to gain unauthorized access to Bamboo servers, potentially escalating privileges to the system level. The vulnerability affects continuous integration and deployment environments where Bamboo is used, potentially allowing attackers to access source code repositories, modify build processes, or exfiltrate sensitive data. Organizations using older versions of Bamboo may experience unauthorized access to their development infrastructure, leading to supply chain compromises and potential data breaches. The attack surface is particularly wide given that Bamboo is commonly used in enterprise environments where it may have access to sensitive corporate resources and systems.
Mitigation strategies for CVE-2016-5229 focus primarily on upgrading to patched versions of Atlassian Bamboo, specifically versions 5.11.4.1 or 5.12.3.1 and later. Organizations should also implement network-level restrictions to limit access to Bamboo servers, particularly disabling external access to the serialization endpoints. Additional defensive measures include configuring XStream to use a whitelist of permitted classes, implementing proper input validation for serialized data, and monitoring for suspicious deserialization activities. Security teams should also consider implementing intrusion detection systems that can identify patterns associated with deserialization attacks. The vulnerability highlights the importance of proper serialization security practices and demonstrates how seemingly innocuous library configurations can create significant security risks. Organizations should conduct thorough security assessments of their software dependencies to identify similar vulnerabilities that may exist in other applications using similar serialization frameworks.