Detect Adobe Acrobat Use-After-Free Exploitation (CVE-2020-9715) in Microsoft Sentinel
Detects exploitation of CVE-2020-9715, a use-after-free vulnerability in Adobe Acrobat that allows arbitrary code execution. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog and has been actively exploited in the wild. Attackers typically deliver malicious PDF documents that trigger memory corruption upon rendering, leading to code execution in the context of the Acrobat process.
MITRE ATT&CK
KQL Detection Query
let AcrobatProcs = dynamic(["AcroRd32.exe", "Acrobat.exe", "AcroCEF.exe", "AcroNGL.exe"]);
let SuspChildProcs = dynamic(["cmd.exe", "powershell.exe", "wscript.exe", "cscript.exe", "mshta.exe", "rundll32.exe", "regsvr32.exe", "certutil.exe", "bitsadmin.exe", "msiexec.exe", "wmic.exe"]);
DeviceProcessEvents
| where TimeGenerated > ago(7d)
| where InitiatingProcessFileName in~ (AcrobatProcs)
| where FileName in~ (SuspChildProcs)
| project TimeGenerated, DeviceName, AccountName, InitiatingProcessFileName, InitiatingProcessCommandLine, FileName, ProcessCommandLine, InitiatingProcessParentFileName
| extend AlertDetail = strcat("Adobe Acrobat spawned suspicious child process: ", FileName)
| order by TimeGenerated descDetects Adobe Acrobat spawning suspicious child processes consistent with use-after-free exploitation leading to code execution. Targets Microsoft Defender for Endpoint telemetry.
Data Sources
Required Tables
False Positives & Tuning
- Acrobat plugins or extensions that legitimately spawn helper processes
- IT automation tools that invoke Acrobat via command line and chain other processes
- Security scanning tools that open PDFs and inspect spawned processes
Other platforms for CVE-2020-9715
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 Acrobat UAF — Malicious PDF Spawning cmd.exe
Expected signal: Sysmon Event ID 1 showing cmd.exe with ParentImage path containing AcroRd32; DeviceProcessEvents entry in MDE with InitiatingProcessFileName = AcroRd32_sim.exe and FileName = cmd.exe
- Test 2Simulate Acrobat UAF — PowerShell Payload Execution
Expected signal: Sysmon Event ID 1 for powershell.exe with suspicious parent; DeviceProcessEvents capturing PowerShell command-line with -ExecutionPolicy Bypass flag
- Test 3Simulate Acrobat UAF — Executable Drop to Temp Directory
Expected signal: Sysmon Event ID 11 (FileCreate) for executable written to %TEMP%; Sysmon Event ID 1 for process launch from %TEMP% path; MDE DeviceFileEvents and DeviceProcessEvents entries
- Test 4Simulate Acrobat UAF — Outbound C2 Beacon Simulation
Expected signal: Sysmon Event ID 3 (NetworkConnect) for outbound connection to non-RFC1918 IP on non-standard port; DeviceNetworkEvents in MDE capturing the destination IP and port
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