12-Year-Old PostgreSQL Vulnerability Enables Database, Server Takeover

Summary

A severe vulnerability in PostgreSQL, dubbed PostGREShell (CVE-2026-6471), has been discovered, allowing attackers with 'Replication' privileges to gain remote code execution and permanent superuser access. The flaw, present in versions since 2014, exploits a missing authorization in the logical decoding process, enabling attackers to load and execute arbitrary files with the privileges of the PostgreSQL system user. This can lead to a full database and server takeover, including the deployment of persistent backdoor mechanisms.

Full text

PostgreSQL releases since 2014 contain a severe vulnerability that allows attacker with low privileges to take over databases and servers, cybersecurity firm Cyera reports. An open source relational database system offering support for both relational (SQL) and non-relational (JSON) queries, PostgreSQL is one of the most popular databases, being used by tens of thousands of companies, including large enterprises. Tracked as CVE-2026-6471 (CVSS score of 7.2) and referred to as PostGREShell, the recently identified security defect can be exploited for remote code execution and privilege escalation. It is described as a missing authorization in the database’s logical decoding and can be exploited by attackers that have ‘Replication’ privileges to load any file visible to the OS account running the server, via the logical decoding plugin. PostgreSQL, Cyera explains, uses a dedicated replication protocol to sync multiple replicas of any primary database, for backup and recovery. An account with the Replication attribute is required for that, and one is provided to any connected backup tool, server, pipeline, and monitoring utility. Changes are recorded by local replication as table events, so that external tools can read, which they do by creating a logical replication slot and naming an output plugin that is loaded by PostgreSQL to format the stream.Advertisement. Scroll to continue reading. When a plugin is loaded, PostgreSQL runs their init function with the privileges of the server process. To prevent abuse, non-superusers can only load plugins from an admin-controlled directory. Cyera discovered that the plugin’s name is passed directly to the loader, without validation or sanitization, which allows an attacker to hand the loader a full filesystem path that is served to dlopen(), the C/C++ function used to dynamically load shared libraries. “The replication protocol’s parser accepts almost any character inside a double-quoted plugin name: slashes, backslashes, dots, ../ traversal, even Windows UNC paths,” Cyera notes. This allows an attacker to load and execute any file through dlopen(), and the file is executed with the privileges of the postgres system user. “Code loaded via dlopen() runs in the same address space as PostgreSQL, with no sandbox and no checks on internal API calls. The server simply trusts any code that was loaded,” Cyera explains. “So the plugin calls an internal function to become the bootstrap superuser for the session, then writes directly to pg_authid, the catalog table that defines who is a superuser, and flips every privilege flag to true,” the company continues. At this point, the attacker has obtained permanent superuser privileges: they can access every table in every database, execute OS commands, read private keys, and write files to any location the postgres process has access to. According to Cyera, the plugin can also deploy backdoor mechanisms: it can enable connections without passwords, copies itself to a stable location and registers itself to be re-loaded into every new backend, and can re-apply the superuser change even if it is reverted. “PostGREShell turns the Replication credential nobody worries about into code execution, superuser, and a persistent backdoor on the database behind much of the internet. Every version from 9.4 through 18 is affected (we confirmed it on 18.2), and logical replication is now standard production plumbing, so the vulnerable path exists almost everywhere PostgreSQL runs,” Cyera notes. CVE-2026-6471 has been patched in PostgreSQL versions 18.6, 17.11, 16.15, 15.19, and 14.24. Organizations are advised to update their instances as soon as possible, audit their Replication accounts, and remove the Replication attribute from any account that does not need it. Related: Rockwell Automation Patches Over a Dozen Vulnerabilities Across Products Related: OpenLeash Adds a Human Check to Risky AI Agent Actions Related: Threat Actor Hacks 14,000 IP Cameras in Ukraine and Russia Related: New HollowGraph Malware Abuses Microsoft 365 Calendar for C&C Communication Written By Ionut Arghire Ionut Arghire is an international correspondent for SecurityWeek. 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Indicators of Compromise

• cve — CVE-2026-6471

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