CVE-2026-86930

claris filemaker server

score 30CRITICAL 9.1

Summary

An out-of-bounds read vulnerability in FileMaker Server for Linux allowed an attacker uploading a specially crafted image file to a container field to disclose process memory during thumbnail generation in FileMaker WebDirect. This vulnerability is addressed in FileMaker Server version 26.0.3.

Published 2026-09-23 · first seen here 2026-10-10

Analysis & write-ups

No technical write-up from a research team yet. Contact Zero checks Unit 42, Google/Mandiant, Microsoft, Talos, CrowdStrike, Rapid7, watchTowr and others several times a day, plus NVD and CISA reference links.

Where it shows in your logs

Endpoint OS (macOS, iOS, Linux, Android) · Memory corruption (overflow, use-after-free) high confidence

What to look for

Crashes or restarts of the vulnerable process (Windows Error Reporting, core dumps), especially repeated ones
The vulnerable process spawning children it never normally starts
Unexpected root processes or shells started by services
New persistence: launch agents/daemons (macOS), cron jobs or systemd units (Linux)
Outbound connections to rare destinations from system processes

Data sources

Process creation · ATT&CK DS0009 Process Creation

Sentinel: DeviceProcessEventsSecurityEvent (4688)Sysmon Event ID 1_Im_ProcessCreate
Splunk: Endpoint.ProcessesXmlWinEventLog:Microsoft-Windows-Sysmon/OperationalWinEventLog:Security (4688)
CrowdStrike: ProcessRollup2SyntheticProcessRollup2

File creation · ATT&CK DS0022 File Creation

Sentinel: DeviceFileEventsSysmon Event ID 11_Im_FileEvent
Splunk: Endpoint.FilesystemSysmon Event ID 11
CrowdStrike: NewExecutableWrittenNewScriptWritten*FileWritten events

Network connections · ATT&CK DS0029 Network Connection Creation / Network Traffic Flow

Sentinel: DeviceNetworkEventsCommonSecurityLog (firewall)_Im_NetworkSession
Splunk: Network_Traffic.All_TrafficFirewall sourcetypes (pan:traffic, fortigate_traffic, cisco:asa)
CrowdStrike: NetworkConnectIP4NetworkReceiveAcceptIP4NetworkConnectIP6