Detect Synacor Zimbra Collaboration Suite PHP Remote File Inclusion (CVE-2025-68645) in CrowdStrike LogScale
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
LogScale Detection Query
event_simpleName IN ("ProcessRollup2", "NetworkConnectIP4", "PeFileWritten", "ScriptControlScanTelemetry")
| eval is_zimbra_host=if(match(ComputerName, "zimbra") OR match(LocalAddressIP4, "zimbra"), 1, 0)
| eval is_rfi_url=if(
match(CommandLine, "(?i)(include|require|include_once|require_once).{0,100}https?://")
OR match(TargetFileName, "/opt/zimbra/(data/tmp|store|index)/.*\.php$"),
1, 0)
| eval is_php_outbound=if(
match(ImageFileName, "(?i)/usr/bin/php|/usr/local/bin/php")
AND match(CommandLine, "(?i)https?://"),
1, 0)
| eval is_webshell_indicator=if(
match(TargetFileName, "/opt/zimbra/") AND match(TargetFileName, "\.php$")
AND NOT match(TargetFileName, "/opt/zimbra/(lib|zimlets|conf)/"),
1, 0)
| where is_rfi_url=1 OR is_php_outbound=1 OR is_webshell_indicator=1
| stats count by timestamp, ComputerName, UserName, CommandLine, ImageFileName, TargetFileName, LocalAddressIP4, RemoteAddressIP4
| sort -timestampCrowdStrike CQL query detecting Zimbra ZCS PHP RFI exploitation through PHP process command-line RFI patterns, unexpected PHP file writes in Zimbra data directories, and PHP process outbound HTTP connections.
Data Sources
Required Tables
False Positives & Tuning
- Zimbra-related PHP processes performing legitimate outbound API calls to update services
- Zimlet deployment processes writing PHP extension files to Zimbra directories
- Scheduled Zimbra maintenance scripts creating PHP stub files in temporary directories
- CrowdStrike sensor telemetry noise from high-frequency PHP-FPM request processing
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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Get the full detection package for CVE-2025-68645 including response playbook, investigation guide, and atomic red team tests.