CVE-2018-1000185 in GitHub Branch Source Plugin
Summary
by MITRE
A server-side request forgery vulnerability exists in Jenkins GitHub Branch Source Plugin 2.3.4 and older in Endpoint.java that allows attackers with Overall/Read access to cause Jenkins to send a GET request to a specified URL.
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Analysis
by VulDB Data Team • 07/16/2020
The vulnerability described in CVE-2018-1000185 represents a critical server-side request forgery flaw within the Jenkins GitHub Branch Source Plugin version 2.3.4 and earlier. This issue stems from improper input validation in the Endpoint.java component which fails to adequately sanitize user-supplied URLs. The vulnerability specifically affects systems where attackers possess Overall/Read access permissions, which typically grants them the ability to view Jenkins configuration and job details but not modify them directly. This access level is commonly granted to developers and team members who need to monitor build processes but should not have the capability to execute arbitrary network requests.
The technical implementation of this vulnerability occurs when Jenkins processes requests related to GitHub repository endpoints without sufficient validation of the target URLs. Attackers can exploit this by crafting malicious requests that specify arbitrary URLs for Jenkins to fetch data from, potentially enabling them to access internal network resources that would normally be protected from external access. The flaw essentially allows an attacker to use Jenkins as an intermediary to make HTTP GET requests to targets within the internal network, bypassing traditional network security controls. This type of vulnerability falls under the CWE-918 category of Server-Side Request Forgery, which is classified as a critical security weakness in web applications.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to perform reconnaissance activities against internal systems, potentially leading to further exploitation opportunities. An attacker could leverage this vulnerability to probe internal services, identify running applications, or even attempt to exploit other vulnerabilities in internal systems that are not directly exposed to the internet. The risk is particularly elevated in environments where Jenkins operates within corporate networks with segmented security zones, as the compromised Jenkins instance could serve as a stepping stone for lateral movement attacks. This vulnerability aligns with ATT&CK technique T1071.004 for Application Layer Protocol: DNS, and could contribute to broader attack chains involving internal network reconnaissance and privilege escalation.
Organizations should immediately upgrade to Jenkins GitHub Branch Source Plugin version 2.3.5 or later, which contains the necessary patches to address this vulnerability. Additionally, implementing network segmentation controls and restricting Jenkins access to only necessary GitHub endpoints can help mitigate the risk. Security teams should also monitor Jenkins logs for suspicious outbound network requests and implement proper input validation measures throughout their Jenkins configurations. The vulnerability demonstrates the importance of validating all external inputs and implementing proper access controls, as even read-only access permissions can be exploited to create significant security risks in CI/CD environments.