CVE-2020-25694: PostgreSQL Information Disclosure Flaw

CVE-2020-25694 Overview

A security flaw has been identified in PostgreSQL that affects how client applications handle database connection parameters. When a client application creates additional database connections by reusing only basic connection parameters while dropping security-relevant parameters, it creates an opportunity for man-in-the-middle attacks or the ability to observe clear-text transmissions. This vulnerability poses a significant threat to data confidentiality, integrity, and system availability.

Critical Impact

Organizations running vulnerable PostgreSQL versions may be susceptible to man-in-the-middle attacks that could expose sensitive database communications and allow attackers to intercept or modify data in transit.

Affected Products

• PostgreSQL versions before 13.1
• PostgreSQL versions before 12.5, 11.10, 10.15, 9.6.20, and 9.5.24
• Debian Linux 9.0

Discovery Timeline

• November 16, 2020 - CVE-2020-25694 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-25694

Vulnerability Analysis

This vulnerability (CWE-327: Use of a Broken or Risky Cryptographic Algorithm) stems from improper handling of security parameters during database connection establishment. When PostgreSQL client applications create secondary connections, they may fail to properly propagate security-critical connection parameters such as SSL/TLS settings, certificate validation options, or authentication mechanisms. This creates a window where subsequent connections may be established with weaker security configurations than intended.

The flaw is particularly concerning in environments where applications maintain connection pools or establish multiple connections to the database server. An attacker positioned on the network path between the client and server could exploit this weakness to intercept database traffic that should have been encrypted or authenticated.

Root Cause

The root cause lies in how the PostgreSQL client library handles connection parameter inheritance when spawning new connections. Security-relevant parameters that enforce encrypted communications or certificate validation may be inadvertently dropped when the application only passes basic connection parameters (such as host, port, and database name) to new connection requests. This design oversight results in connections that bypass the intended security posture.

Attack Vector

The attack vector is network-based and requires the attacker to be positioned to intercept traffic between the PostgreSQL client and server. The exploitation scenario involves:

1. A client application establishes an initial secure connection to PostgreSQL with proper SSL/TLS and authentication parameters
2. The application creates additional connections but only passes basic parameters, dropping security settings
3. The new connections may be established without encryption or proper certificate validation
4. An attacker conducting a man-in-the-middle attack can intercept these insecure connections
5. The attacker gains visibility into database queries and responses, potentially capturing sensitive data or injecting malicious commands

The vulnerability can be exploited when an attacker has network-level access to intercept communications. Connection pooling implementations and applications that dynamically create database connections are particularly at risk. Database administrators should review client application code to ensure all security-relevant connection parameters are consistently applied across all connection instances.

Detection Methods for CVE-2020-25694

Indicators of Compromise

• Unexpected unencrypted PostgreSQL traffic on port 5432 when SSL should be enforced
• Certificate validation warnings or bypass attempts in PostgreSQL client logs
• Connection attempts with missing or inconsistent security parameters
• Network traffic analysis showing mixed encrypted and unencrypted database communications

Detection Strategies

• Monitor network traffic for unencrypted PostgreSQL protocol communications using tools like Wireshark or tcpdump
• Implement database audit logging to track connection security parameters and identify connections established without expected SSL/TLS
• Review application connection pooling configurations for proper security parameter propagation
• Deploy network intrusion detection systems (IDS) to identify potential man-in-the-middle attack patterns

Monitoring Recommendations

• Enable PostgreSQL server logging for connection parameters including sslmode and authentication methods
• Configure alerts for connections that do not use expected encryption levels
• Periodically audit client application code for proper connection parameter handling
• Monitor for anomalous database connection patterns that may indicate exploitation attempts

How to Mitigate CVE-2020-25694

Immediate Actions Required

• Upgrade PostgreSQL to patched versions: 13.1, 12.5, 11.10, 10.15, 9.6.20, or 9.5.24 or later
• Review and update client applications to ensure security parameters are passed to all database connections
• Enforce SSL/TLS at the PostgreSQL server level by configuring hostssl entries in pg_hba.conf
• Audit connection pooling implementations for proper security parameter inheritance

Patch Information

PostgreSQL has released security updates addressing this vulnerability. Organizations should upgrade to the following minimum versions:

• PostgreSQL 13.1 or later
• PostgreSQL 12.5 or later
• PostgreSQL 11.10 or later
• PostgreSQL 10.15 or later
• PostgreSQL 9.6.20 or later
• PostgreSQL 9.5.24 or later

For official security information and download links, consult the PostgreSQL Security Support Page. Debian users should refer to the Debian LTS Security Announcement for distribution-specific guidance.

Workarounds

• Configure PostgreSQL server to reject non-SSL connections by removing host entries and using only hostssl in pg_hba.conf
• Implement network-level encryption (IPsec or VPN) between clients and database servers as an additional layer of protection
• Use connection string validation in applications to ensure security parameters are always present
• Consider implementing mutual TLS (mTLS) for database connections to enforce certificate-based authentication

# Configuration example - Enforce SSL connections in pg_hba.conf
# Replace existing 'host' entries with 'hostssl' to require SSL
# Example pg_hba.conf entries:
hostssl    all    all    0.0.0.0/0    scram-sha-256
hostssl    all    all    ::/0         scram-sha-256

# Set ssl=on in postgresql.conf
ssl = on
ssl_cert_file = '/path/to/server.crt'
ssl_key_file = '/path/to/server.key'
ssl_ca_file = '/path/to/ca.crt'