CVE-2020-2253 in Email Extension Plugin
Summary
by MITRE
Jenkins Email Extension Plugin 2.75 and earlier does not perform hostname validation when connecting to the configured SMTP server.
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Analysis
by VulDB Data Team • 09/16/2020
The vulnerability identified as CVE-2020-2253 affects the Jenkins Email Extension Plugin version 2.75 and earlier, presenting a critical security flaw in the plugin's handling of SMTP server connections. This issue stems from the absence of proper hostname validation during the establishment of secure communication channels with external mail servers. The flaw allows attackers to potentially manipulate the email delivery process by redirecting communications to unauthorized SMTP servers, thereby compromising the integrity and confidentiality of email notifications generated by Jenkins.
The technical implementation of this vulnerability resides in the plugin's network communication layer where it establishes connections to SMTP servers without verifying the server's identity through proper hostname validation. This weakness creates a path for man-in-the-middle attacks where malicious actors can intercept or redirect email communications intended for legitimate recipients. The vulnerability aligns with CWE-295 which specifically addresses improper certificate validation and hostname verification in network communications. When Jenkins attempts to send email notifications, the plugin connects to the configured SMTP server using standard SMTP protocols but fails to validate that the server's certificate matches the expected hostname, leaving the system exposed to various attack vectors.
The operational impact of this vulnerability extends beyond simple email delivery failures, as it can enable sophisticated attack scenarios that compromise the overall security posture of Jenkins environments. Attackers can exploit this weakness to intercept sensitive build notifications, credentials, or system alerts that contain confidential information. The vulnerability particularly affects organizations that rely heavily on Jenkins for continuous integration and deployment processes, where email notifications often contain critical information about build statuses, security alerts, or deployment confirmations. This flaw can facilitate information disclosure attacks where attackers gain access to system information that would normally be protected within the secure email delivery infrastructure of the CI/CD pipeline.
Organizations should immediately upgrade to Jenkins Email Extension Plugin version 2.76 or later to remediate this vulnerability, as this release includes proper hostname validation mechanisms. Security administrators should also implement additional monitoring to detect unauthorized SMTP server configurations or unexpected email delivery patterns. The mitigation strategy should include regular security assessments of all Jenkins plugins and their configurations, ensuring that network communication protocols maintain proper certificate validation. Organizations may also consider implementing network-level controls such as firewall rules that restrict outbound SMTP connections to approved servers, thereby reducing the attack surface. This vulnerability demonstrates the importance of maintaining up-to-date software components and implementing defense-in-depth strategies that protect against credential exposure and information disclosure threats. The issue also aligns with ATT&CK technique T1566 which covers social engineering through email, as compromised email delivery can facilitate further attacks on the broader network infrastructure.