CVE-2023-39417: PostgreSQL SQL Injection Vulnerability

CVE-2023-39417 Overview

A SQL Injection vulnerability was identified in PostgreSQL affecting extension scripts that utilize @extowner@, @extschema@, or @extschema:...@ substitution parameters inside quoting constructs such as dollar quoting, single quotes (''), or double quotes (""). This vulnerability enables an attacker with database-level CREATE privilege to inject malicious SQL code through vulnerable, trusted, non-bundled extensions that have been installed by an administrator, potentially leading to arbitrary code execution with bootstrap superuser privileges.

Critical Impact

Attackers with CREATE privilege on a PostgreSQL database can escalate to full superuser access by exploiting SQL injection in vulnerable extension scripts, enabling complete database compromise and arbitrary code execution.

Affected Products

• PostgreSQL (multiple versions)
• Red Hat Software Collections
• Red Hat Enterprise Linux 8.0 and 9.0
• Debian Linux 8.0, 11.0, and 12.0

Discovery Timeline

• August 11, 2023 - CVE-2023-39417 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-39417

Vulnerability Analysis

This SQL Injection vulnerability (CWE-89) exists within PostgreSQL's extension installation mechanism. PostgreSQL extensions use substitution parameters like @extowner@, @extschema@, and @extschema:...@ within their installation scripts to dynamically reference the extension owner and schema at installation time. When these parameters are used within quoting constructs (dollar quoting, single quotes, or double quotes), insufficient sanitization allows attackers to break out of the intended quoting context and inject arbitrary SQL statements.

The vulnerability specifically affects third-party trusted extensions that are not bundled with PostgreSQL's core distribution. When an administrator installs such a vulnerable extension, any user with CREATE privilege on the database can craft malicious inputs that, when processed by the extension's installation script, result in SQL injection. Since extension installation runs with superuser privileges, successful exploitation grants the attacker bootstrap superuser access to the PostgreSQL instance.

Root Cause

The root cause lies in PostgreSQL's handling of substitution parameter expansion within extension scripts. When @extowner@, @extschema@, or @extschema:...@ values are substituted into SQL statements that are already within quoting constructs, the substituted values are not properly escaped or validated. This allows carefully crafted schema names or owner specifications to include characters that terminate the quoting construct and append arbitrary SQL commands. The trust model assumes extension scripts are safe, but this assumption breaks when user-controllable data flows into these substitution parameters without adequate sanitization.

Attack Vector

The attack is network-accessible and requires only low-privileged database access with CREATE permission. An attacker must identify a PostgreSQL instance where an administrator has installed a vulnerable third-party trusted extension. The attacker can then exploit the vulnerability by manipulating the extension installation process or by crafting inputs that trigger the vulnerable code path during extension operations.

The attack does not require user interaction beyond the initial conditions (a vulnerable extension being installed). Once these conditions are met, the attacker can execute arbitrary SQL as the bootstrap superuser, potentially:

• Creating new superuser accounts
• Reading, modifying, or deleting any data in the database
• Executing operating system commands via PostgreSQL's copy program or other mechanisms
• Installing persistent backdoors within the database

-- Conceptual illustration of vulnerable pattern in extension scripts
-- A vulnerable extension might contain patterns like:
CREATE FUNCTION @extschema@.vulnerable_function()
  RETURNS void AS $$
  -- SQL code here referencing @extowner@ or @extschema@
  $$ LANGUAGE sql;

-- When @extschema@ is not properly sanitized and contains
-- malicious input, the quoting construct can be escaped,
-- allowing arbitrary SQL injection with superuser privileges.

Detection Methods for CVE-2023-39417

Indicators of Compromise

• Unusual extension installation or modification activities in PostgreSQL logs
• Unexpected superuser account creation or privilege escalation events
• Database audit logs showing CREATE EXTENSION commands with unusual schema or owner values
• Modifications to system catalogs or extension-related tables from non-administrative users

Detection Strategies

• Monitor PostgreSQL server logs for extension-related operations, particularly CREATE EXTENSION statements with unusual parameters
• Implement database activity monitoring to detect privilege escalation patterns or unexpected superuser operations
• Review installed extensions using \dx or querying pg_extension to identify non-bundled third-party extensions that may be vulnerable
• Deploy SentinelOne Singularity Platform for real-time monitoring of PostgreSQL process behavior and anomalous database activities

Monitoring Recommendations

• Enable detailed PostgreSQL logging including log_statement = 'all' and log_min_messages = 'info' during security audits
• Configure alerting for any superuser-level operations performed by non-administrative database roles
• Regularly audit the list of installed PostgreSQL extensions and their sources
• Implement network segmentation to restrict database access to authorized application servers only

How to Mitigate CVE-2023-39417

Immediate Actions Required

• Apply the latest PostgreSQL security updates from your distribution vendor immediately
• Audit all installed PostgreSQL extensions and identify any non-bundled third-party extensions
• Review and restrict database-level CREATE privileges to only essential accounts
• Consider temporarily disabling or removing untrusted third-party extensions until patches are applied

Patch Information

PostgreSQL and major Linux distributions have released patches addressing this vulnerability. Administrators should apply updates from their respective vendors:

• PostgreSQL: Security patches available via the PostgreSQL Security Advisory
• Red Hat: Multiple security advisories including RHSA-2023:7545, RHSA-2023:7579, and additional updates for Enterprise Linux 8 and 9
• Debian: Security advisories DSA-5553 and DSA-5554 provide patched packages
• NetApp: Advisory NTAP-20230915-0002 covers affected NetApp products

Workarounds

• Restrict CREATE privilege on databases to only trusted administrative accounts until patches can be applied
• Remove or disable non-essential third-party PostgreSQL extensions, particularly those from untrusted sources
• Implement strict network access controls to limit database connectivity to authorized hosts only
• Use PostgreSQL's row-level security and role-based access control to minimize the impact of potential privilege escalation

# Review installed extensions and their trust status
psql -c "SELECT extname, extversion, extowner::regrole FROM pg_extension;"

# Revoke CREATE privilege from non-administrative roles
psql -c "REVOKE CREATE ON DATABASE your_database FROM public;"
psql -c "REVOKE CREATE ON DATABASE your_database FROM untrusted_role;"

# List users with superuser privileges for audit
psql -c "SELECT usename, usesuperuser FROM pg_user WHERE usesuperuser = true;"