Detect Synacor Zimbra Collaboration Suite PHP Remote File Inclusion (CVE-2025-68645) in Elastic Security
Detects exploitation of CVE-2025-68645, a PHP Remote File Inclusion (RFI) vulnerability in Synacor Zimbra Collaboration Suite (ZCS). CWE-98 class vulnerabilities allow attackers to inject and execute remote PHP files via unsanitized user-controlled input passed to PHP file inclusion functions, enabling arbitrary code execution in the context of the web server process. This vulnerability is listed in the CISA Known Exploited Vulnerabilities catalog.
MITRE ATT&CK
- Tactic
- Initial Access Execution Persistence
Elastic Detection Query
sequence by host.name with maxspan=5m
[network where event.type == "connection" and
destination.port in (80, 443, 8080, 8443) and
process.name in ("php", "php-fpm", "php7.4", "php8.0", "php8.1", "php8.2") and
(
http.request.referrer : "*=http*" or
url.query : "*=http*" or
url.query : "*=ftp://*" or
url.query : "*=php://input*"
)]
[file where event.type == "creation" and
file.path : "/opt/zimbra/*" and
file.extension == "php" and
not file.path : "/opt/zimbra/lib/*" and
not file.path : "/opt/zimbra/zimlets/*"]EQL sequence correlation: first detects PHP process making outbound connections with RFI-pattern URL parameters, then correlates with unexpected PHP file creation in Zimbra directories within a 5-minute window.
Data Sources
Required Tables
False Positives & Tuning
- Zimbra upgrade scripts that create PHP files in data directories as part of patching
- Custom Zimlet deployments writing PHP files to non-standard paths
- PHP-FPM health checks that incidentally create temporary files
- Monitoring agents instrumenting Zimbra PHP processes for performance metrics
Other platforms for CVE-2025-68645
Testing Methodology
Validate this detection against 4 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 PHP RFI via HTTP Request Parameter Injection
Expected signal: Web server access log entry with URL parameter containing http://attacker.lab/malicious.php; network connection attempt from PHP process to attacker.lab:80
- Test 2Create Simulated Web Shell in Zimbra Data Directory
Expected signal: File creation event for /opt/zimbra/data/tmp/lab_test/shell_test_atomic.php; auditd syscall event for open/write by test user
- Test 3PHP Process Invoking Remote File Fetch (RFI Simulation)
Expected signal: Process telemetry showing php binary with command-line containing http:// URL; network connection attempt from php process to 127.0.0.1:9999 (or external IP in real attack)
- Test 4Zimbra Config File Access by Non-Zimbra Process (Post-Exploitation Credential Harvest)
Expected signal: Auditd open/read syscall event on /opt/zimbra/conf/localconfig.xml by non-zimbra UID; file access timestamp update visible in stat output
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