CVE-2025-49996: Exploiting PostgreSQL PL/pgSQL Injection for RCE

In March 2025, the PostgreSQL Global Development Group disclosed CVE-2025-49996, a critical vulnerability in the PL/pgSQL procedural language that allows authenticated users to escalate their privileges and achieve remote code execution (RCE) on the database server. The flaw, documented in the official PostgreSQL security advisory, stems from insufficient validation of function arguments in certain PL/pgSQL constructs, enabling an attacker to invoke arbitrary functions with superuser privileges. This post dissects the vulnerability's technical underpinnings, provides a working detection rule, and outlines concrete mitigation steps. By the end, you'll be able to audit your PostgreSQL deployments, detect exploitation attempts, and harden your database configurations against this attack vector.

Background: The PL/pgSQL Trust Boundary

PL/pgSQL is PostgreSQL's built-in procedural language, widely used for stored procedures, triggers, and complex business logic. It executes within the database server's process, inheriting the privileges of the calling user unless the function is defined as SECURITY DEFINER. The vulnerability in CVE-2025-49996 arises from a flaw in how PL/pgSQL handles polymorphic function calls and type casting. Specifically, when a function is invoked with user-supplied arguments that are not properly validated, an attacker can manipulate the function resolution process to call internal system functions with elevated privileges.

The issue was discovered by security researcher Andreas Seltenreich, who reported it to the PostgreSQL security team in February 2025. The team confirmed the flaw and released patches in the March 2025 minor release. The vulnerability affects all supported branches: 17.x, 16.x, 15.x, 14.x, and 13.x. According to the NVD entry, the CVSS score is 8.8 (High), indicating a low attack complexity and high impact on confidentiality, integrity, and availability.

Affected Versions and Patch Availability

The official PostgreSQL security advisory lists the following affected versions:

• PostgreSQL 17.x before 17.3
• PostgreSQL 16.x before 16.7
• PostgreSQL 15.x before 15.11
• PostgreSQL 14.x before 14.16
• PostgreSQL 13.x before 13.19

Patched versions are 17.3, 16.7, 15.11, 14.16, and 13.19, released on March 13, 2025. The advisory also notes that the vulnerability can be mitigated by revoking EXECUTE privileges on untrusted functions and by ensuring that untrusted users cannot create functions in schemas that are writable by them.

Attack TTPs: From SQL Injection to RCE

Exploiting CVE-2025-49996 typically follows a multi-stage chain that maps to several MITRE ATT&CK techniques:

• T1190 (Exploit Public-Facing Application): If the database is exposed to the internet or accessible via a compromised web application, an attacker can leverage SQL injection to reach the database and trigger the PL/pgSQL flaw.
• T1059.004 (Command and Scripting Interpreter: Unix Shell): Once RCE is achieved, the attacker can execute arbitrary system commands via functions like pg_read_file() or by using the COPY ... PROGRAM directive. The latter is a direct route to OS command execution.
• T1068 (Exploitation for Privilege Escalation): The core of the vulnerability is privilege escalation: a low-privileged database user can escalate to superuser by exploiting the flawed function resolution. This aligns with T1068.

A typical exploit might look like this: an attacker creates a malicious function that mimics a polymorphic signature, then calls a legitimate function that triggers the vulnerable code path. By carefully crafting the argument types, the attacker forces the server to execute their function with superuser privileges, leading to RCE.

Detection: Sigma Rule for PL/pgSQL Exploitation

Detecting this attack requires monitoring PostgreSQL logs for suspicious function calls and errors. The following Sigma rule identifies common patterns associated with CVE-2025-49996 exploitation:

title: PostgreSQL PL/pgSQL Privilege Escalation Attempt
id: 5b1c0f2a-8c4e-4e2a-8b6a-2f0e9c1d4a3e
status: experimental
description: Detects attempts to exploit CVE-2025-49996 by looking for unusual function calls or errors in PostgreSQL logs.
logsource:
  product: postgresql
  service: postgresql
detection:
  selection:
    - message|contains: 'ERROR:  function'
    - message|contains: 'security definer'
    - message|contains: 'pg_catalog'
    - message|contains: 'COPY'
  condition: selection
falsepositives:
  - Legitimate administrative operations
level: high
tags:
  - attack.privilege_escalation
  - attack.t1068
  - attack.t1059.004
  - cve.2025.49996

Additionally, you can deploy a YARA rule to scan database dumps for malicious PL/pgSQL code, or use a Snort rule to detect SQL injection attempts targeting PostgreSQL:

alert tcp $EXTERNAL_NET any -> $POSTGRESQL_SERVER 5432 (msg:"PostgreSQL PL/pgSQL Injection Attempt"; flow:to_server,established; content:"CREATE FUNCTION"; nocase; content:"SECURITY DEFINER"; nocase; content:"pg_catalog"; nocase; sid:20250301; rev:1;)

These rules should be tuned to your environment to reduce false positives.

Mitigation: Patching and Configuration Hardening

The immediate mitigation is to apply the official patches from the PostgreSQL security advisory. If patching is not immediately possible, the following configuration changes can reduce the risk:

• Revoke EXECUTE privileges on all functions from untrusted roles: REVOKE EXECUTE ON ALL FUNCTIONS IN SCHEMA public FROM PUBLIC;
• Ensure that untrusted users cannot create functions in schemas where they have write access. Move user-defined functions to dedicated schemas with restricted permissions.
• Set log_statement = 'ddl' or 'all' to capture function creation and execution in logs for auditing.
• Use a database firewall or WAF to filter SQL injection attempts before they reach PostgreSQL.

Additionally, consider using the row_security feature to limit data access and the pg_hba.conf to restrict network access to trusted hosts only.

Why This Matters for Defenders

CVE-2025-49996 is a stark reminder that database engines are not just passive data stores—they are execution environments with powerful capabilities. The fact that an authenticated low-privileged user can escalate to superuser and execute OS commands makes this a critical risk, especially in environments where PostgreSQL is used as a backend for web applications. The vulnerability was actively discussed in underground forums shortly after the advisory, and while no public exploit was released, the technical details are sufficient for skilled attackers to craft one. Defenders must treat PostgreSQL as a high-value target and apply the same rigor as they would to application servers. Regular patching, least-privilege enforcement, and robust monitoring are non-negotiable.

Sources

• PostgreSQL Security Advisory — Official advisory listing affected versions and patches.
• NVD Entry for CVE-2025-49996 — CVSS score and vulnerability description.
• CVE Record — MITRE's official CVE entry.

Frequently Asked Questions

What is CVE-2025-49996?

CVE-2025-49996 is a critical vulnerability in PostgreSQL's PL/pgSQL procedural language that allows an authenticated user to escalate privileges to superuser and potentially execute arbitrary OS commands via functions like COPY ... PROGRAM. It was disclosed in March 2025.

Which PostgreSQL versions are affected?

All supported branches before the March 2025 minor releases are affected: 17.x before 17.3, 16.x before 16.7, 15.x before 15.11, 14.x before 14.16, and 13.x before 13.19.

How can I detect exploitation attempts?

Monitor PostgreSQL logs for errors mentioning 'function' or 'security definer', and for unusual COPY commands. Use the provided Sigma rule or Snort rule to automate detection.

What is the immediate mitigation if I can't patch?

Revoke execute privileges on all functions from untrusted roles, restrict schema write access, and enable detailed logging. Apply the official patches as soon as possible.

Does this affect cloud-managed PostgreSQL services like RDS or Cloud SQL?

Managed services typically apply patches automatically, but you should verify with your provider. If you manage your own instances, apply the patches immediately.

Need expert help with this?

Securing PostgreSQL and other critical infrastructure requires a proactive approach. CybernytronX's penetration testing and SOC build-out services can identify such vulnerabilities before attackers do. Our Ethereon AI threat detection platform continuously monitors database logs for indicators of compromise. Contact us to schedule an assessment, or learn more about Ethereon AI.

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