CVE-2016-4983 in Dovecot
Summary
by MITRE
A postinstall script in the dovecot rpm allows local users to read the contents of newly created SSL/TLS key files.
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Analysis
by VulDB Data Team • 09/29/2024
The vulnerability identified as CVE-2016-4983 resides within the dovecot package's postinstall script implementation on rpm-based Linux systems. This flaw represents a critical security oversight in the handling of cryptographic key material during package installation processes. The vulnerability specifically affects systems where dovecot is installed using rpm packages, creating a window of opportunity for local privilege escalation and information disclosure attacks.
The technical mechanism behind this vulnerability involves the improper handling of file permissions within the postinstall script execution phase. During the installation of dovecot, the package manager executes a postinstall script that generates new SSL/TLS key files for secure email communication. However, this script fails to properly set restrictive file permissions on these newly created key files, leaving them accessible to local users who may not have legitimate access to cryptographic material. The vulnerability stems from the script's lack of proper umask settings or explicit chmod operations that would normally secure sensitive key files immediately after creation. This design flaw creates a race condition where newly generated keys remain world-readable until the system administrator manually corrects permissions or the next system reboot occurs.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally compromises the security posture of mail servers utilizing dovecot. Local users who can execute the postinstall script can extract cryptographic keys used for SSL/TLS encryption, potentially enabling man-in-the-middle attacks, session hijacking, or even full system compromise if these keys are used for authentication purposes. The vulnerability affects all systems running vulnerable versions of dovecot packages where the postinstall script executes with sufficient privileges to create key files. Attackers could leverage this to gain unauthorized access to email communications, potentially intercepting sensitive data transmitted through the mail server. The implications are particularly severe in enterprise environments where dovecot serves as a core component of email infrastructure and where multiple users may have local access to the system.
This vulnerability aligns with CWE-732: Incorrect Permission Assignment for Critical Resource, which specifically addresses inadequate permission settings for security-critical files. The flaw also maps to ATT&CK technique T1068: Exploitation for Privilege Escalation, as local users can exploit this weakness to gain access to sensitive cryptographic material that could then be used for further attacks. Additionally, the vulnerability demonstrates characteristics of T1552: Unsecured Credentials, as it exposes cryptographic keys that should remain protected. Organizations should immediately update their dovecot packages to versions that address this postinstall script issue and implement proper file permission management during package installation processes. System administrators should also conduct thorough audits of existing key files to ensure no unauthorized access has occurred, and consider implementing additional monitoring for suspicious file access patterns related to cryptographic materials. The remediation process requires careful attention to package management procedures and ensures that all newly created key files are immediately secured with restrictive permissions to prevent similar issues in the future.