Detect Synacor Zimbra Collaboration Suite PHP Remote File Inclusion (CVE-2025-68645) in Microsoft Sentinel
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
KQL Detection Query
union DeviceNetworkEvents, DeviceProcessEvents
| where TimeGenerated > ago(7d)
| where (DeviceName contains "zimbra" or InitiatingProcessCommandLine contains "zimbra" or FolderPath contains "/opt/zimbra")
| where (
(ActionType == "InboundConnectionAccepted" and RemoteUrl matches regex @"(?i)(https?://[^/]+/.*\.(php|txt|jpg|png|gif)\?.*=https?://|file://|ftp://)")
or (ProcessCommandLine matches regex @"(?i)(include|require|include_once|require_once)\s*\(.*https?://")
or (InitiatingProcessCommandLine matches regex @"(?i)curl\s.*-o.*\.php|wget\s.*\.php|fetch.*http")
or (FolderPath matches regex @"/opt/zimbra/(data/tmp|store|index)/.*\.php$")
)
| project TimeGenerated, DeviceName, ActionType, ProcessCommandLine, InitiatingProcessCommandLine, RemoteUrl, FolderPath, AccountName, RemoteIP
| order by TimeGenerated descDetects PHP Remote File Inclusion exploitation attempts against Zimbra ZCS by correlating inbound HTTP requests with RFI-pattern URLs and unexpected PHP file creation in Zimbra data directories.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate administrative scripts using PHP include with local paths that superficially match regex patterns
- Zimbra automated backup or migration tasks that fetch remote content via curl/wget
- Security scanners performing vulnerability assessments against Zimbra endpoints
- Development environments where PHP files are legitimately fetched for testing purposes
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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