CVE-2017-9514 in Bamboo
Summary
by MITRE
Bamboo before 6.0.5, 6.1.x before 6.1.4, and 6.2.x before 6.2.1 had a REST endpoint that parsed a YAML file and did not sufficiently restrict which classes could be loaded. An attacker who can log in to Bamboo as a user is able to exploit this vulnerability to execute Java code of their choice on systems that have vulnerable versions of Bamboo.
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Analysis
by VulDB Data Team • 01/16/2021
The vulnerability identified as CVE-2017-9514 represents a critical deserialization flaw in Atlassian Bamboo continuous integration server that affected multiple version ranges including pre-6.0.5, 6.1.x pre-6.1.4, and 6.2.x pre-6.2.1. This vulnerability resides within Bamboo's REST API endpoint responsible for processing YAML configuration files, creating a pathway for remote code execution attacks. The flaw stems from insufficient class loading restrictions during YAML parsing operations, allowing malicious actors to leverage the deserialization process to execute arbitrary Java code on affected systems.
The technical implementation of this vulnerability leverages Java's deserialization mechanism, where the REST endpoint accepts YAML input and attempts to convert it into Java objects. Without proper class validation or whitelisting, the system becomes vulnerable to object deserialization attacks that can load malicious classes from remote sources. This weakness directly maps to CWE-502, which specifically addresses deserialization of untrusted data, and aligns with ATT&CK technique T1059.007 for execution through Java deserialization. The vulnerability is particularly dangerous because it requires only user-level authentication to exploit, meaning any authenticated user with access to Bamboo can potentially compromise the entire system.
From an operational impact perspective, this vulnerability creates a severe security risk for organizations relying on Bamboo for continuous integration and deployment processes. Attackers who gain access to legitimate user accounts can execute arbitrary code on build servers, potentially leading to full system compromise, data exfiltration, and disruption of development workflows. The vulnerability affects not just individual build agents but can compromise the entire Bamboo server infrastructure, as the executed code runs with the privileges of the Bamboo service account. This risk is compounded by the fact that many organizations use Bamboo for automated deployments, making the potential impact of exploitation significantly broader than typical application vulnerabilities.
Organizations should immediately upgrade to patched versions of Bamboo, specifically versions 6.0.5, 6.1.4, or 6.2.1, respectively, to remediate this vulnerability. Network segmentation and access controls should be implemented to limit user access to the Bamboo REST endpoints where possible. Additionally, monitoring should be enhanced to detect unusual deserialization activities or unauthorized access attempts to Bamboo's configuration endpoints. The vulnerability demonstrates the critical importance of proper input validation and secure deserialization practices, particularly in enterprise applications handling configuration data from external sources. Security teams should also consider implementing application firewalls or Web Application Firewalls to filter potentially malicious YAML content before it reaches the vulnerable parsing components, while ensuring that any authentication tokens or session management remains robust against session hijacking attempts that could lead to exploitation.