CVE-2018-20936 in cPanel
Summary
by MITRE
cPanel before 68.0.27 allows attackers to read the SRS secret via exim.conf (SEC-308).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2018-20936 represents a critical information disclosure flaw in cPanel versions prior to 68.0.27 that directly impacts email server security configurations. This vulnerability specifically affects the Exim mail transfer agent configuration file exim.conf where the SRS (Sender Rewriting Scheme) secret is improperly exposed, creating a significant security risk for organizations relying on cPanel for their email infrastructure management.
The technical flaw stems from insufficient access controls and configuration management within the cPanel administrative interface. When cPanel generates or manages Exim configurations, it fails to properly restrict access to sensitive parameters including the SRS secret key. This secret key serves as a cryptographic element used in email address rewriting mechanisms that help prevent spam and maintain email deliverability. The vulnerability allows authenticated attackers with appropriate privileges to access the exim.conf file and extract this critical secret, potentially enabling them to forge email addresses or bypass spam filtering mechanisms.
The operational impact of this vulnerability extends beyond simple information disclosure, as the SRS secret can be leveraged to perform sophisticated email manipulation attacks. Attackers who obtain this secret can potentially rewrite sender addresses in email headers, making it appear as though messages originate from legitimate sources. This capability directly relates to attack patterns described in the MITRE ATT&CK framework under the T1566 technique for Phishing and T1071 for Application Layer Protocol usage. The vulnerability creates opportunities for credential theft, social engineering campaigns, and reputation damage to affected organizations.
Organizations should immediately implement the patch released in cPanel version 68.0.27 which properly restricts access to sensitive configuration parameters and ensures that SRS secrets are not exposed in publicly accessible configuration files. Additionally, administrators should conduct thorough audits of their Exim configurations to verify that no other sensitive information has been inadvertently exposed through similar configuration flaws. Network segmentation and access control measures should be reinforced to limit administrative access to critical system files, while monitoring systems should be configured to detect unauthorized access attempts to configuration files. The vulnerability aligns with CWE-200, which addresses improper exposure of sensitive information, and represents a clear failure in secure configuration management practices that organizations must address through comprehensive security hardening procedures.