Possible FortiGate RCE via Chunked hostcheck_validate Request (CVE-2024-21762)

ATT&CK techniques

Initial Access

Recon
Resource Dev
Initial Access
- T1190Exploit Public-Facing Application
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects POST requests to the FortiGate SSL VPN hostcheck_validate endpoint using Transfer-Encoding chunked, matching the out-of-bounds write exploited in CVE-2024-21762 as analyzed by Assetnote. The exploit relies on a malformed chunked body with a zero-length terminator and excess trailer lines to corrupt memory and reach code execution. Detecting chunked requests to this specific endpoint surfaces attempts against the vulnerable parser.

Reporting behind it

Related detections9 linkedT1190 — drag to rearrange

Malicious Command Shell Spawned by SQL Server via Process Creation (via process_creation)

Malicious Command Shell or PowerShell Spawned by Tomcat via Process Creation (via process_creation)

Suspicious Shell Script Execution From Temp Directory on SonicWall SMA1000 Appliance (via process_creation)

Possible TP-Link Command Injection via WlanNetworkRpm Endpoint (via webserver)

Malicious SharePoint ToolPane Exploitation via SignOut Referer

Suspicious Tomcat Session Deserialization Trigger via Crafted JSESSIONID

Malicious Tomcat Partial PUT of Session File via Content-Range Header

Malicious Ivanti Connect Secure Path Traversal Exploitation of CVE-2024-21887

Malicious MOVEit moveitisapi Exploitation Request via webserver

Possible FortiGate RCE via Chunked hostcheck_validate Request (CVE-2024-21762)

Pivot detection · T1190 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

Full detection rule

Unlock this rule to view and copy it

The detection logic is included with a plan. Everything else — context, mappings and implementation details — stays free on this page.

Sign in for 3 free unlocks

Signing in gives you 3 unlocks to spend on any rule in the library. No card, and they do not expire.

Also included

Unlocked rules convert on this page — to Splunk SPL or Splunk — Raw Index SPL or Microsoft Sentinel KQL or Microsoft Sentinel ASIM ASIM KQL or Microsoft Defender XDR KQL or Elastic Security KQL or Elastic Security Lucene or Elastic Security ES|QL or CrowdStrike Falcon CQL or SentinelOne PowerQuery or Palo Alto Cortex XDR XQL or Carbon Black Cloud Platform Search or Carbon Black EDR Process Search or Google Security Operations UDM Search or IBM QRadar AQL or Sumo Logic Cloud SIEM Rules expression or Rapid7 InsightIDR LEQL or Graylog Search or OpenSearch Lucene or OpenSearch PPL PPL or Grafana Loki LogQL or SQLite SQL or Zircolite SQLite — with the log-source profile the engine picked, the field map it used, and everything it could not express. Converting a rule you have unlocked costs no further credit.

See it run on a free rule →Convert your own rule →