Detect Balbooa Forms Unrestricted File Upload Exploitation (CVE-2026-56291) in Splunk
Detects exploitation attempts against CVE-2026-56291, an unrestricted upload of file with dangerous type vulnerability (CWE-434) in Balbooa Forms for Joomla. This vulnerability is listed in CISA KEV, indicating confirmed active exploitation. Attackers abuse the forms file upload functionality to upload web shells or other malicious executable content (PHP, PHTML, PHAR, etc.) bypassing extension/type restrictions, leading to remote code execution on the underlying web server.
MITRE ATT&CK
- Tactic
- Initial Access Execution
SPL Detection Query
index=web sourcetype=access_combined OR sourcetype=iis
(uri_path="*com_balbooaforms*" OR uri_path="*balbooa*")
method=POST
| rex field=uri_path "(?<uploaded_file>[^/\\\\]+\.(?<ext>php\d?|phtml|phar|pht|jsp|asp|aspx))"
| where isnotnull(ext)
| stats count min(_time) as first_seen max(_time) as last_seen by clientip, uri_path, uploaded_file, status, http_user_agent
| where count > 0Searches web server access logs for POST requests to Balbooa Forms endpoints uploading files with dangerous executable extensions, indicating CVE-2026-56291 exploitation.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Benign file uploads with php-like strings embedded in unrelated filenames
- Automated vulnerability scanners performing authorized security testing
- Load balancer health checks against the forms component
Other platforms for CVE-2026-56291
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Simulate dangerous file extension upload POST request
Expected signal: Web server access log entry showing POST request to com_balbooaforms upload endpoint with filename test_shell.php and 200/201 status code.
- Test 2Upload double-extension bypass file (.phtml)
Expected signal: Web access log entry for POST request with mismatched Content-Type (image/jpeg) and .phtml extension in filename.
- Test 3Windows IIS-hosted Joomla upload simulation
Expected signal: W3CIISLog entry recording POST to com_balbooaforms endpoint with cs-uri-stem containing test_shell.aspx.
References (4)
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