CVE-2026-77137: Backend Module SQL Injection Vulnerability

CVE-2026-77137 Overview

CVE-2026-77137 is a SQL injection vulnerability [CWE-89] affecting a TYPO3 extension that exposes a "Forms Export" backend module. The extension fails to sanitize user-supplied input before incorporating it into a database query. An authenticated low-privileged backend user with read access to the Forms Export module can inject arbitrary SQL through a URL parameter. Successful exploitation compromises the confidentiality, integrity, and availability of the underlying database.

Critical Impact
An authenticated backend user can execute arbitrary SQL statements against the TYPO3 database, enabling data theft, unauthorized modification, and destructive operations against stored records.

Affected Products

TYPO3 third-party extension providing the "Forms Export" backend module (see TYPO3 Security Advisory #2026-027)
Deployments exposing the affected module to non-administrative backend users
Any TYPO3 installation where the vulnerable extension version is installed and enabled

Discovery Timeline

2026-08-25 - CVE-2026-77137 published to NVD
2026-08-26 - Last updated in NVD database

Technical Details for CVE-2026-77137

Vulnerability Analysis

The vulnerability resides in the request-handling logic of the Forms Export backend module. The extension reads a URL parameter and concatenates or interpolates it directly into a SQL query without parameterization or escaping. This flaw maps to CWE-89, Improper Neutralization of Special Elements used in an SQL Command.

An attacker with a valid low-privileged backend account can craft a malicious URL parameter that terminates the intended query fragment and appends attacker-controlled SQL. Because TYPO3 backend modules run with database credentials that typically have full read and write access to the TYPO3 schema, the injected statements execute against every table the connection can reach. Consult the TYPO3 Security Advisory #2026-027 for the affected code path and fixed versions.

Root Cause

The root cause is missing input sanitization and the absence of prepared statements. Instead of binding user input as query parameters, the affected code path composes SQL strings with untrusted values sourced from a URL parameter within the Forms Export module.

Attack Vector

Exploitation is remote over the network but requires an authenticated backend session and read access to the Forms Export module. No user interaction is required beyond the attacker's own request. An attacker submits an HTTP request to the backend endpoint with a manipulated URL parameter carrying a SQL payload, which the extension then executes against the TYPO3 database.

No verified public exploit code is available at the time of publication. The vulnerability mechanics are described in prose in the vendor advisory rather than through published proof-of-concept code.

Detection Methods for CVE-2026-77137

Indicators of Compromise

Backend HTTP requests to Forms Export module endpoints containing SQL metacharacters such as single quotes, UNION, SELECT, --, /*, or ; inside URL parameters.
Unexpected database queries originating from backend user sessions that reference tables outside the Forms Export scope, such as be_users or sys_registry.
Backend audit log entries showing repeated access to the Forms Export module by non-administrative users, especially with unusual query strings.

Detection Strategies

Enable TYPO3 backend logging and database query logging, then alert on Forms Export requests whose parameters contain SQL syntax tokens.
Deploy a web application firewall rule set that inspects authenticated backend traffic for SQL injection patterns targeting the module route.
Correlate low-privileged backend account activity with anomalous database read volume or access to sensitive tables.

Monitoring Recommendations

Monitor authentication and authorization events for backend users granted access to the Forms Export module and review access grants on a regular schedule.
Track outbound data volumes from the TYPO3 database host to identify potential bulk extraction that follows successful injection.
Forward TYPO3 backend and web server logs to a centralized analytics platform to enable retrospective hunting once a patch or signature is available.

How to Mitigate CVE-2026-77137

Immediate Actions Required

Apply the fixed extension release identified in TYPO3 Security Advisory #2026-027 as soon as it is available in your environment.
Audit backend user accounts and revoke access to the Forms Export module for any user who does not require it.
Rotate credentials for backend accounts that had access to the module, and review database logs for evidence of prior injection attempts.

Patch Information

The TYPO3 project publishes fixed versions of affected extensions through the TYPO3 Extension Repository. Review TYPO3 Security Advisory #2026-027 for the specific extension name, vulnerable version range, and fixed version. Update using Composer or the Extension Manager and verify the installed version after deployment.

Workarounds

Restrict backend user permissions so that only trusted administrators can read the Forms Export module until patching completes.
Place the TYPO3 backend behind an IP allowlist, VPN, or authenticated reverse proxy to reduce exposure of the vulnerable endpoint.
Configure a web application firewall to block SQL injection payloads on requests to the Forms Export module route.

bash

# Example: update the affected TYPO3 extension via Composer
composer update vendor/forms-export-extension --with-dependencies
./vendor/bin/typo3 extension:list | grep -i forms
./vendor/bin/typo3 cache:flush