Detect CVE-2026-48062: CodeIgniter4 File Upload Extension Validation Bypass (ext_in Rule) in IBM QRadar
CVE-2026-48062 affects CodeIgniter4 framework versions prior to 4.7.2. The `ext_in` validation rule fails to properly validate file extensions during upload, allowing attackers to bypass extension restrictions and upload arbitrary files including web shells or malicious executables. This unrestricted file upload vulnerability (CWE-434) has a CVSS score of 9.8 and a public proof-of-concept. Successful exploitation can lead to remote code execution on the hosting server.
MITRE ATT&CK
- Tactic
- Initial Access Execution Persistence
QRadar Detection Query
SELECT DATEFORMAT(starttime, 'YYYY-MM-dd HH:mm:ss') AS event_time,
sourceip,
destinationip,
URL,
username,
"File Name",
"File Path",
magnitude,
category
FROM events
WHERE (category = 5018 OR category = 5019 OR LOGSOURCETYPENAME(devicetype) IN ('Apache HTTP Server', 'Nginx', 'PHP-FPM'))
AND (
(URL MATCHES '(?i).*(upload|writable|public|tmp|cache).*\.(php[0-9]?|phtml|phar|shtml|pht)$')
OR ("File Path" MATCHES '(?i).*(upload|writable|public).*' AND "File Name" MATCHES '(?i).*\.(php[0-9]?|phtml|phar|shtml|pht)$')
)
AND QIDNAME(qid) NOT ILIKE '%allowed%'
LAST 7 DAYS
ORDER BY starttime DESC
LIMIT 500QRadar AQL query detecting HTTP requests and file events involving suspicious script extensions in CodeIgniter4 upload paths, correlating web access logs with file creation events to surface potential ext_in bypass exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Authorized content management operations uploading PHP template components
- Administrative file management through web-based control panels
- Penetration testing activities against the web application with prior authorization
- False extension matching on legitimate filenames containing PHP-like substrings
Other platforms for CVE-2026-48062
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 CodeIgniter4 ext_in Bypass via Crafted Multipart Upload
Expected signal: HTTP POST to upload endpoint with Content-Type image/jpeg but .php file extension; file creation event in upload directory for a .php file; web server process as the initiating process for the file write
- Test 2Web Shell Execution Verification After Upload
Expected signal: HTTP GET requests to PHP file path in upload directory; process tree showing web server (apache2/nginx/php-fpm) spawning shell or system binaries (id, whoami, uname); network connections to external IP if reverse shell payload used
- Test 3Filesystem Reconnaissance via Uploaded Web Shell
Expected signal: Process events for cat, ls, find spawned by php-fpm or apache2 with web server UID; file read events on /etc/passwd and .env files initiated by web server process; auditd SYSCALL records for execve by www-data user
References (6)
- https://github.com/codeigniter4/CodeIgniter4/security/advisories/GHSA-2gr4-ppc7-7mhx
- https://github.com/codeigniter4/CodeIgniter4/commit/29299349e7d232e9532767c7cefaed30957309be
- https://codeigniter.com/user_guide/libraries/uploaded_files.html#moving-files
- https://codeigniter.com/user_guide/libraries/validation.html#rules-for-file-uploads
- https://github.com/codeigniter4/CodeIgniter4/blob/develop/CHANGELOG.md
- https://github.com/advisories/GHSA-2gr4-ppc7-7mhx
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