CVE-2017-7547 in PostgreSQL
Summary
by MITRE
PostgreSQL versions before 9.2.22, 9.3.18, 9.4.13, 9.5.8 and 9.6.4 are vulnerable to authorization flaw allowing remote authenticated attackers to retrieve passwords from the user mappings defined by the foreign server owners without actually having the privileges to do so.
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Analysis
by VulDB Data Team • 01/09/2021
The vulnerability described in CVE-2017-7547 represents a critical authorization flaw within PostgreSQL database systems that affects multiple major versions including 9.2.21 and earlier, 9.3.17 and earlier, 9.4.12 and earlier, 9.5.7 and earlier, and 9.6.3 and earlier. This flaw specifically targets the foreign data wrapper functionality that allows PostgreSQL to access external data sources through user mappings defined by foreign server owners. The vulnerability enables remote authenticated attackers to bypass normal access controls and retrieve passwords from user mappings that should only be accessible to authorized users with appropriate privileges.
The technical nature of this flaw stems from insufficient validation of user permissions when accessing user mappings associated with foreign servers. In PostgreSQL's foreign data wrapper implementation, user mappings define the credentials that are used to connect to external data sources through foreign servers. When an attacker authenticates to the PostgreSQL system with valid credentials, they can exploit this authorization bypass to access password information from user mappings that belong to foreign server owners. This occurs because the system fails to properly verify whether the authenticated user has legitimate access rights to the specific user mappings they are attempting to query. The flaw essentially allows privilege escalation through unauthorized access to sensitive credential information.
The operational impact of this vulnerability is significant as it undermines the fundamental security model of PostgreSQL's access control mechanisms. Attackers who can authenticate to the database system can potentially extract passwords for foreign server connections, which may provide them with access to additional systems or data sources. This creates a potential attack vector that could lead to lateral movement within network environments where PostgreSQL serves as a gateway to external databases or services. The vulnerability particularly affects organizations that rely heavily on foreign data wrappers to integrate with external systems, as the extracted passwords could grant access to critical backend systems. The remote nature of the attack means that authenticated users in the network can exploit this flaw without requiring physical access to the database server.
Organizations should immediately apply the security patches released by PostgreSQL for versions 9.2.22, 9.3.18, 9.4.13, 9.5.8, and 9.6.4 to address this vulnerability. The fix involves implementing proper access control checks when retrieving user mappings from foreign servers, ensuring that only authorized users can access the password information associated with specific user mappings. System administrators should also conduct thorough audits of foreign server configurations and user mappings to identify any potential unauthorized access that may have occurred. Additionally, implementing network segmentation and monitoring for unusual database access patterns can help detect potential exploitation attempts. This vulnerability aligns with CWE-284 which describes improper access control issues, and could be categorized under ATT&CK technique T1078 for valid accounts and T1566 for credential access, highlighting the multi-layered security implications of such authorization bypasses.