Detect iCagenda Unrestricted File Upload Exploitation (CVE-2026-48939) in Google Chronicle
Detects exploitation attempts against CVE-2026-48939, an Unrestricted Upload of File with Dangerous Type vulnerability (CWE-434) in the iCagenda Joomla component. Attackers abuse insufficient file-type validation in iCagenda's upload handlers (event image/attachment upload endpoints) to upload web shells or other executable content, achieving remote code execution on the underlying web server. This CVE is listed in CISA KEV, indicating confirmed active exploitation and mandated remediation under BOD 26-04.
MITRE ATT&CK
- Tactic
- Initial Access Execution
YARA-L Detection Query
rule icagenda_cve_2026_48939_upload {
meta:
author = "detection-platform"
description = "Detects suspicious file upload to iCagenda Joomla component consistent with CVE-2026-48939"
severity = "HIGH"
events:
$e.metadata.event_type = "NETWORK_HTTP"
$e.network.http.method = "POST"
$e.target.url = /.*com_icagenda.*/ nocase
$e.target.url = /.*(upload|attachment|image).*/ nocase
$e.target.url = /.*\.(php\d?|phtml|phar|pht|asp|aspx|jsp)$/ nocase
match:
$e over 5m
condition:
$e
}Chronicle YARA-L rule detecting POST-based upload requests to iCagenda endpoints with dangerous file extensions, aligned to CVE-2026-48939 exploitation TTPs.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate administrative uploads
- Automated compliance scanners
- Proxy replays of cached upload requests
Other platforms for CVE-2026-48939
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 malicious PHP upload to iCagenda endpoint
Expected signal: Web server access log entry showing POST to com_icagenda upload path with HTTP 200 response, followed by a new file creation event in the media/com_icagenda upload directory
- Test 2Verify uploaded shell executability
Expected signal: GET request to the uploaded PHP file logged, followed by php-fpm/apache2 spawning a child process (id) consistent with web shell command execution
- Test 3Windows IIS-hosted Joomla upload simulation
Expected signal: W3C IIS log entry recording POST to com_icagenda upload endpoint with dangerous .aspx extension and 200 status
References (4)
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