CVE-2020-2189 in SCM Filter Jervis Plugin
Summary
by MITRE
Jenkins SCM Filter Jervis Plugin 0.2.1 and earlier does not configure its YAML parser to prevent the instantiation of arbitrary types, resulting in a remote code execution vulnerability.
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Analysis
by VulDB Data Team • 05/07/2020
The vulnerability identified as CVE-2020-2189 affects the Jenkins SCM Filter Jervis Plugin version 0.2.1 and earlier, presenting a critical remote code execution risk through improper YAML parsing configuration. This issue stems from the plugin's failure to properly restrict type instantiation during YAML deserialization processes, creating an avenue for malicious actors to execute arbitrary code on affected Jenkins servers. The flaw exists within the plugin's handling of YAML input data, which is commonly used for configuration management and data exchange within continuous integration environments.
The technical root cause of this vulnerability lies in the plugin's YAML parser implementation which lacks proper type filtering mechanisms. When the plugin processes YAML content, it fails to restrict the instantiation of arbitrary Java classes, allowing attackers to craft malicious YAML payloads that can trigger the deserialization of dangerous objects. This behavior aligns with CWE-502, which describes deserialization of untrusted data vulnerabilities, and represents a classic example of insecure deserialization that enables remote code execution. The vulnerability is particularly dangerous because Jenkins servers often run with elevated privileges, making successful exploitation capable of compromising entire build environments and potentially leading to broader system compromise.
The operational impact of CVE-2020-2189 extends beyond simple remote code execution, as it enables attackers to gain persistent access to Jenkins environments that are typically considered trusted within organizational networks. Attackers can leverage this vulnerability to execute arbitrary commands on the Jenkins server, potentially leading to data exfiltration, privilege escalation, and further lateral movement within the network. The vulnerability affects Jenkins installations that utilize the SCM Filter Jervis plugin, particularly those configured to process untrusted YAML input from external sources or user-controlled data streams. This risk is exacerbated by the fact that Jenkins environments often contain sensitive build scripts, credentials, and access controls that can be leveraged for more extensive attacks.
Mitigation strategies for CVE-2020-2189 primarily focus on immediate plugin updates and configuration hardening measures. Organizations should upgrade to Jenkins SCM Filter Jervis Plugin version 0.2.2 or later, which includes proper YAML parser configuration to prevent arbitrary type instantiation. Additionally, administrators should implement network segmentation to limit access to Jenkins servers, enforce strict input validation for all YAML processing, and consider implementing additional security controls such as Jenkins security plugins that can further restrict deserialization operations. From an ATT&CK framework perspective, this vulnerability maps to techniques involving deserialization attacks and remote code execution, emphasizing the need for defensive measures that monitor and restrict potentially dangerous deserialization operations within CI/CD environments. The vulnerability also underscores the importance of maintaining up-to-date security practices in automated build systems where the compromise of a single component can provide attackers with extensive access to development infrastructure and sensitive organizational data.