CVE-2026-85620 in postgres-mcp
Summary
by MITRE • 09/04/2026
Postgres MCP Pro 0.3.0 contains a restricted-mode bypass vulnerability where function-name validation is not applied to RangeFunction nodes in FROM clauses. Attackers can execute file-reading functions like pg_read_file through FROM-clause syntax to read arbitrary files despite restricted-mode protections.
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Analysis
by VulDB Data Team • 09/04/2026
The vulnerability identified in Postgres MCP Pro version 0.3.0 represents a critical security flaw rooted in the incomplete implementation of access control mechanisms within the database engine's query parser and execution layer. Specifically, the system employs a restricted mode designed to limit user capabilities for enhanced security, yet this protection mechanism fails to enforce function-name validation on RangeFunction nodes when they appear within FROM clauses of SQL queries. This architectural oversight allows an attacker to bypass intended restrictions by leveraging specific syntactic constructs that are not adequately sanitized or checked against the allowed functions list. The core technical flaw lies in the disparity between how standard SELECT-list expressions and table-generating functions from the FROM clause are processed, with the latter lacking the necessary validation checks present elsewhere in the query execution pipeline.
From a technical perspective, this vulnerability enables unauthorized file system access through the exploitation of PostgreSQL's built-in superuser-level function pg_read_file. Under normal circumstances, restricted-mode configurations should prevent users without elevated privileges from invoking functions that interact directly with the operating system's file I/O subsystems. However, because the validation logic does not inspect RangeFunction nodes in FROM clauses, an attacker can construct a malicious query that utilizes this syntax to invoke pg_read_file indirectly or directly depending on how the parser resolves the range function. This effectively neutralizes the security boundary established by the restricted mode, allowing the reading of arbitrary files from the server's file system where the database process has read permissions.
The operational impact of this vulnerability is severe, as it leads to a complete compromise of data confidentiality and potentially integrity depending on subsequent exploitation steps. An attacker with limited access can exfiltrate sensitive configuration files, application source code containing hardcoded credentials, private keys, or other critical data stored in the file system. This bypass undermines the principle of least privilege, which is fundamental to secure database administration. Furthermore, if combined with other vulnerabilities such as SQL injection or weak authentication, this flaw could serve as a pivot point for deeper network intrusion, allowing attackers to escalate privileges and move laterally within the infrastructure. The ability to read arbitrary files also facilitates reconnaissance activities where attackers gather information about the underlying operating system version, installed software, and directory structures to plan further attacks.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. Immediately, administrators should upgrade Postgres MCP Pro to a patched version that corrects the validation logic for RangeFunction nodes in FROM clauses. Until an update is available, restricting database user privileges to the absolute minimum required can reduce exposure, although this may not fully mitigate the issue if the attacker already possesses sufficient permissions to execute queries within the restricted mode context. Implementing Web Application Firewalls or query filters that detect and block attempts to use pg_read_file in FROM clauses can provide a temporary defensive layer. Long-term solutions involve conducting a comprehensive code review of the access control module, ensuring that all entry points for function execution undergo consistent validation against an allow-list of permitted functions. Additionally, adopting defense-in-depth principles by isolating database processes from sensitive file systems and using operating system-level permissions to restrict read/write access can limit the blast radius even if such vulnerabilities are exploited in the future.
This vulnerability aligns with Common Weakness Enumeration (CWE) categories such as CWE-284 Improper Access Control, which describes situations where an actor is able to access resources or functionality that they should not be allowed to, and CWE-798 Use of Hard-coded Credentials if the accessed files contain sensitive information. In terms of the MITRE ATT&CK framework, this exploit maps to T1005 Data from Local System, which covers techniques used by adversaries to collect data directly from a compromised host using command-line interfaces or scripts that read local files. Understanding these mappings helps in categorizing the risk and aligning remediation efforts with industry-standard security practices for database protection and incident response planning.