CVE-2026-40906: ElectricSQL SQLi Vulnerability

CVE-2026-40906 Overview

CVE-2026-40906 is a critical SQL injection vulnerability affecting Electric, a Postgres sync engine. The vulnerability exists in the order_by parameter of the ElectricSQL /v1/shape API, which fails to properly sanitize user input. This error-based SQL injection flaw allows any authenticated user to read, write, and destroy the full contents of the underlying PostgreSQL database through crafted ORDER BY expressions.

Critical Impact

Authenticated attackers can achieve complete database compromise including data exfiltration, modification, and destruction through malicious ORDER BY expressions in the ElectricSQL API.

Affected Products

• ElectricSQL versions 1.1.12 through 1.4.x
• Electric Postgres sync engine prior to version 1.5.0
• Systems using the vulnerable /v1/shape API endpoint

Discovery Timeline

• 2026-04-21 - CVE-2026-40906 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-40906

Vulnerability Analysis

This SQL injection vulnerability (CWE-89: Improper Neutralization of Special Elements used in an SQL Command) affects the ElectricSQL /v1/shape API endpoint. The vulnerability arises from insufficient input validation and sanitization of the order_by parameter, which is directly incorporated into SQL queries without proper parameterization or escaping.

Error-based SQL injection allows attackers to extract information from the database by triggering SQL errors that reveal data in error messages. In this case, authenticated users can craft malicious ORDER BY expressions that manipulate the underlying PostgreSQL queries to perform unauthorized operations beyond simple data retrieval—including data modification and deletion.

The scope of this vulnerability is particularly concerning because it affects the PostgreSQL synchronization layer, meaning that compromised data could propagate across synchronized clients and systems.

Root Cause

The root cause is improper input validation in the order_by parameter handling within the /v1/shape API. The parameter value is concatenated directly into SQL query construction without proper sanitization, parameterized queries, or allowlist validation. This allows attackers to break out of the intended ORDER BY context and inject arbitrary SQL commands.

Attack Vector

The attack vector is network-based, requiring only low-privilege authentication to exploit. An attacker with valid credentials can send specially crafted HTTP requests to the /v1/shape API endpoint with malicious order_by parameter values. These crafted expressions can:

1. Extract sensitive data through error-based information disclosure
2. Modify existing database records
3. Delete or truncate database tables
4. Potentially escalate privileges within the database context

The vulnerability does not require user interaction and can be automated for large-scale data exfiltration or destruction. See the GitHub Security Advisory for detailed technical analysis.

Detection Methods for CVE-2026-40906

Indicators of Compromise

• Unusual or malformed requests to the /v1/shape API endpoint containing special SQL characters in the order_by parameter
• Database error logs showing SQL syntax errors or unexpected query patterns originating from ElectricSQL
• Unexpected data modifications or deletions in PostgreSQL tables managed by ElectricSQL
• Anomalous database query patterns including UNION SELECT, subqueries, or error-inducing functions in ORDER BY clauses

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect SQL injection patterns in API parameters, specifically targeting ORDER BY injection attempts
• Enable and monitor PostgreSQL query logging for suspicious query patterns containing injection payloads
• Deploy API request logging and anomaly detection for the /v1/shape endpoint
• Configure database activity monitoring to alert on unusual data access patterns or bulk operations

Monitoring Recommendations

• Monitor ElectricSQL application logs for error messages indicating malformed SQL queries
• Set up alerts for database errors related to ORDER BY clause parsing failures
• Track authentication events and correlate with API endpoint access patterns
• Implement rate limiting and request analysis on the /v1/shape API endpoint

How to Mitigate CVE-2026-40906

Immediate Actions Required

• Upgrade ElectricSQL to version 1.5.0 or later immediately
• Audit database activity logs for signs of exploitation prior to patching
• Review and restrict network access to the /v1/shape API endpoint
• Implement input validation at the WAF or reverse proxy level as an additional defense layer

Patch Information

The vulnerability is fixed in ElectricSQL version 1.5.0. The fix implements proper input sanitization and parameterized query handling for the order_by parameter. Organizations should upgrade to version 1.5.0 or later as soon as possible.

For patch details, see the GitHub Pull Request #4081 which contains the security fix.

Workarounds

• Restrict access to the /v1/shape API endpoint to trusted networks only until the patch can be applied
• Implement a reverse proxy or WAF rule to block requests containing SQL injection patterns in the order_by parameter
• Temporarily disable or restrict the order_by functionality if not critical to operations
• Apply database-level permissions to limit the PostgreSQL user account used by ElectricSQL to minimum required privileges

# Example: Restrict database user permissions as defense in depth
# Revoke unnecessary privileges from the ElectricSQL database user
psql -U postgres -c "REVOKE DELETE, DROP ON ALL TABLES IN SCHEMA public FROM electricsql_user;"
psql -U postgres -c "REVOKE TRUNCATE ON ALL TABLES IN SCHEMA public FROM electricsql_user;"