Detect WatchGuard Firebox Out-of-Bounds Write Exploitation (CVE-2025-9242) in Google Chronicle
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
YARA-L Detection Query
rule cve_2025_9242_watchguard_firebox_oob_write {
meta:
author = "df00tech Detection Engineering"
description = "Detects WatchGuard Firebox crash/memory-corruption events indicating potential CVE-2025-9242 exploitation"
severity = "CRITICAL"
priority = "HIGH"
reference = "https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2025-00015"
events:
(
$e.metadata.vendor_name = /(?i)watchguard/ or
$e.metadata.product_name = /(?i)firebox/
)
and (
$e.metadata.description = /(?i)(crash|segfault|out of bounds|write violation|buffer overflow|heap corruption|stack smash|access violation|core dump|fatal error)/ or
$e.principal.labels["raw_message"] = /(?i)(crash|segfault|out of bounds|write violation|buffer overflow|heap corruption)/
)
condition:
$e
}Chronicle YARA-L rule identifying WatchGuard Firebox log events with crash and memory-corruption signatures consistent with CVE-2025-9242 out-of-bounds write exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Firmware update processes on Firebox appliances generating memory-related log entries
- Hardware diagnostics or self-test routines on the Firebox platform
- Excessive legitimate traffic causing resource exhaustion and associated error logs
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.
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