Detect WatchGuard Firebox Out-of-Bounds Write Exploitation (CVE-2025-9242) in Splunk
Detects exploitation attempts targeting CVE-2025-9242, an out-of-bounds write vulnerability (CWE-787) in WatchGuard Firebox appliances. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog, indicating active exploitation in the wild. Successful exploitation may allow remote code execution or denial of service on affected Firebox devices.
MITRE ATT&CK
- Tactic
- Initial Access Execution Impact
SPL Detection Query
index=network (sourcetype=watchguard OR sourcetype=syslog) (source="*watchguard*" OR source="*firebox*" OR vendor="WatchGuard")
| where match(lower(_raw), "crash|segfault|out.of.bounds|write.violation|buffer.overflow|heap.corruption|stack.smash|access.violation|core.dump|fatal.error|exception")
| eval exploit_indicator=case(
match(lower(_raw), "write.violation|out.of.bounds|heap.corruption|stack.smash"), "high",
match(lower(_raw), "crash|segfault|core.dump"), "medium",
match(lower(_raw), "exception|fatal.error"), "low",
true(), "unknown"
)
| stats count AS event_count, values(src_ip) AS source_ips, values(dest_ip) AS dest_ips, earliest(_time) AS first_seen, latest(_time) AS last_seen BY host, exploit_indicator
| where event_count >= 1
| sort - exploit_indicator, - event_countSearches WatchGuard/Firebox log sources for memory-corruption and crash indicators consistent with CVE-2025-9242 out-of-bounds write exploitation. Classifies by severity of indicator keyword.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Scheduled Firebox reboots or planned maintenance generating process crash telemetry
- Firmware update failures that produce memory-error log messages
- ISP-level network storms causing resource exhaustion and crash logs on the Firebox
Other platforms for CVE-2025-9242
Testing Methodology
Validate this detection against 3 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 OOB Write Crash via Malformed Packet to Firebox Management Port
Expected signal: WatchGuard Firebox syslog should show a connection attempt from the test host IP; if the vulnerability is present, a crash or error log entry with memory-violation language should appear within seconds of the payload delivery.
- Test 2WatchGuard Firebox VPN Endpoint Fuzzing
Expected signal: Firebox syslog should record repeated connection attempts from the fuzzer host; if an OOB write is triggered, a crash or process-restart log entry will appear.
- Test 3Verify Firebox Firmware Patch Status via Management API
Expected signal: The management API or CLI returns the current Firebox firmware version string; if the version is below the patched threshold per WGSA-2025-00015, the device is confirmed vulnerable in the lab environment.
Unlock Pro Content
Get the full detection package for CVE-2025-9242 including response playbook, investigation guide, and atomic red team tests.