CVE-2020-29137 in cPanel
Summary
by MITRE • 11/27/2020
cPanel before 90.0.17 allows self-XSS via the WHM Transfer Tool interface (SEC-577).
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Analysis
by VulDB Data Team • 12/10/2020
The vulnerability identified as CVE-2020-29137 represents a self-cross-site scripting flaw within the cPanel software ecosystem, specifically affecting versions prior to 90.0.17. This issue resides within the WHM Transfer Tool interface, which serves as a critical administrative component for system migration and data transfer operations. The vulnerability stems from insufficient input validation and output sanitization mechanisms that fail to properly encode or escape user-supplied data before rendering it within the web interface context. Attackers can exploit this weakness by crafting malicious payloads that, when processed through the transfer tool, execute in the context of authenticated users' browsers. The self-XSS nature indicates that the malicious code is stored within the application's own database or configuration files, making it persistent and potentially exploitable across multiple user sessions.
The technical implementation of this vulnerability demonstrates a classic input sanitization failure that aligns with CWE-79 Cross-site Scripting flaws, specifically categorized under reflected and stored XSS variants. The WHM Transfer Tool interface processes user inputs related to transfer configurations, server addresses, and credential information without adequate sanitization measures. When these inputs are subsequently rendered back to the user interface, the malicious script code executes within the browser context of the authenticated user, potentially leading to session hijacking, privilege escalation, or data exfiltration. The vulnerability is particularly concerning because it operates within a privileged administrative interface where users possess elevated system access rights, amplifying the potential impact of successful exploitation.
The operational impact of CVE-2020-29137 extends beyond simple script execution, as it enables attackers to manipulate the transfer tool's functionality and potentially compromise the entire cPanel installation. An attacker who successfully exploits this vulnerability can modify transfer configurations, redirect data transfers to malicious endpoints, or inject persistent malicious code that executes whenever the transfer tool is accessed. This creates a persistent backdoor within the system that can be leveraged for ongoing surveillance and further exploitation. The vulnerability also poses risks to data integrity and system availability, as malicious actors can manipulate transfer processes to disrupt legitimate operations or cause data corruption. Additionally, the self-XSS characteristic means that the vulnerability can persist across system updates if not properly addressed in the underlying code.
Mitigation strategies for CVE-2020-29137 should prioritize immediate patch application to cPanel versions 90.0.17 and later, which contain the necessary fixes for input validation and output encoding. Organizations should implement comprehensive input sanitization measures that enforce strict validation of all user-supplied data within the WHM Transfer Tool interface, including server addresses, usernames, passwords, and configuration parameters. The implementation of Content Security Policy headers can provide additional defense-in-depth measures to prevent unauthorized script execution. Security monitoring should be enhanced to detect unusual patterns in transfer tool usage, including unexpected parameter modifications or access from unfamiliar IP addresses. Regular security audits of administrative interfaces should be conducted to identify similar sanitization gaps, with particular attention to areas handling user-provided configuration data. Organizations should also consider implementing web application firewalls to monitor and filter potentially malicious inputs before they reach the vulnerable components, while maintaining detailed logging of all transfer tool activities to facilitate incident response and forensic analysis.