CVE-2026-61518 Overview
CVE-2026-61518 is an authenticated SQL injection vulnerability in the ISPConfig Remote API. The primary_id parameter passed to delete and update API methods is concatenated directly into SQL WHERE clauses without integer casting or parameterized query binding. Any authenticated remote API user holding a single low-privilege function permission can inject arbitrary SQL against the control panel database. Attackers can delete or modify records across all tenants and extract sensitive data, including password hashes and client records, through blind boolean inference. The built-in SQL injection scanner fails to block quote-free boolean payloads and does not reject requests under its default configuration.
Critical Impact
A low-privileged Remote API user can read, modify, or delete tenant data across the entire ISPConfig control panel database, including credential hashes.
Affected Products
- ISPConfig control panel (Remote API component)
- Deployments exposing the Remote API endpoint to authenticated users
- Multi-tenant hosting environments using ISPConfig for provisioning
Discovery Timeline
- 2026-08-19 - CVE-2026-61518 published to NVD
- 2026-08-20 - Last updated in NVD database
Technical Details for CVE-2026-61518
Vulnerability Analysis
The vulnerability is a classic SQL injection flaw [CWE-89] in the ISPConfig Remote API. The primary_id parameter, used by delete and update API methods to identify target records, is concatenated directly into SQL WHERE clauses. The application performs no integer casting and does not bind the parameter through prepared statements.
ISPConfig ships a SQL injection scanner intended to filter dangerous input. The scanner does not detect quote-free boolean payloads such as 1 OR 1=1 or time-based boolean inference constructs. In its default configuration, the scanner logs suspicious activity but does not reject the request, so tainted values still reach the database layer.
Exploitation requires only a Remote API account with any single function permission. An attacker with such minimal authorization can pivot from a narrow legitimate scope to full database read, modify, and delete access across every tenant managed by the control panel.
Root Cause
The root cause is missing input validation and unsafe query construction. The primary_id value is expected to be an integer identifier but is used as untrusted string data in dynamic SQL. Parameterized queries or explicit integer casting would eliminate the injection surface.
Attack Vector
An authenticated attacker sends crafted delete or update API requests over the network. The malicious primary_id payload is embedded into the WHERE clause, altering query logic to affect arbitrary rows. Blind boolean inference against the same parameter allows extraction of password hashes, client details, and configuration data without any error output.
No verified public exploit code is included in this advisory. For technical details, refer to the GitHub Documentation and the VulnCheck Security Advisory.
Detection Methods for CVE-2026-61518
Indicators of Compromise
- Remote API requests to delete or update endpoints containing non-integer values in the primary_id parameter.
- ISPConfig SQL injection scanner log entries flagging boolean payloads such as OR 1=1, AND 1=2, or SLEEP( without a corresponding request rejection.
- Unexpected DELETE or UPDATE statements in database query logs referencing tables outside the calling user's tenant scope.
- Sudden mass modification or removal of client, mail, or DNS records not tied to a legitimate administrator session.
Detection Strategies
- Inspect ISPConfig Remote API access logs for primary_id values that are not strictly numeric.
- Enable database query logging and alert on API-originated queries that touch multiple tenant rows in a single statement.
- Correlate low-privilege API session activity with authentication events to identify tokens performing disproportionate data access.
Monitoring Recommendations
- Forward ISPConfig web server, application, and MySQL logs to a centralized analytics platform for correlation.
- Alert on repeated Remote API errors or anomalous response-time patterns consistent with time-based blind SQL injection.
- Baseline normal Remote API usage per account and flag deviations in request volume, endpoint variety, or target record counts.
How to Mitigate CVE-2026-61518
Immediate Actions Required
- Restrict Remote API access to trusted IP addresses using firewall rules or a reverse proxy allowlist.
- Audit Remote API user accounts and revoke unused or excessive function permissions.
- Rotate credentials for all Remote API users and reset ISPConfig client passwords, treating stored hashes as potentially exposed.
- Review database audit logs for unauthorized UPDATE or DELETE activity dating back to before disclosure.
Patch Information
Apply the fixed ISPConfig release referenced in the VulnCheck Security Advisory as soon as it is available. The corrected code path enforces integer casting and parameterized binding for the primary_id parameter across delete and update API methods. Verify the deployed version after upgrading and re-test the Remote API endpoints.
Workarounds
- Disable the Remote API entirely if it is not required for automation or integration workflows.
- Configure the ISPConfig SQL injection scanner to reject, not merely log, suspicious requests where that option is exposed.
- Place the Remote API behind an authenticated reverse proxy or web application firewall that enforces strict integer validation on primary_id.
- Limit each Remote API account to the minimum function permissions required for its automation use case.
# Example firewall restriction limiting Remote API access to a trusted host
iptables -A INPUT -p tcp --dport 8080 -s 10.0.0.25 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
