Skip to content
CVE-2026-76418 IBM QRadar · QRadar

Detect Cisco ASA/FTD Remote Access SSL VPN Unexpected Reload Denial of Service (CVE-2026-76418) in IBM QRadar

Detects exploitation of CVE-2026-76418, an unchecked return value leading to NULL pointer dereference (CWE-690) in the Remote Access SSL VPN service of Cisco Secure Firewall ASA Software and Secure Firewall Threat Defense (FTD) Software. An unauthenticated remote attacker can send crafted requests to a tunnel group that has secondary authentication configured and make the device reload unexpectedly. The CVE is on the CISA KEV catalog (added 2026-10-29, BOD 26-04). Detection focuses on what the firewall and its log pipeline can show: unexpected reload, traceback or crash messages shortly after bursts of unauthenticated WebVPN connections, repeated device restarts in a short window, and a single external source hammering the SSL VPN portal before an outage.

MITRE ATT&CK

Tactic
Impact

QRadar Detection Query

IBM QRadar (QRadar)
sql 
-- df00tech DF00-a7d89fc7d5 · https://df00tech.com/detections/CVE-2026-76418 · licence: https://df00tech.com/detections/licence
SELECT sourceip, QIDNAME(qid) AS event_name, UTF8(payload) AS raw, DATEFORMAT(starttime,'yyyy-MM-dd HH:mm:ss') AS event_time FROM events WHERE LOGSOURCETYPENAME(devicetype) ILIKE '%cisco%' AND (UTF8(payload) ILIKE '%traceback%' OR UTF8(payload) ILIKE '%crashinfo%' OR UTF8(payload) ILIKE '%system restart%' OR UTF8(payload) ILIKE '%reload%') ORDER BY starttime DESC LAST 24 HOURS
high severity low confidence

Returns Cisco ASA or FTD events in QRadar showing crash, restart or reload messages.

Data Sources

Cisco ASA DSMCisco FTD DSM

Required Tables

events

False Positives & Tuning

  • Planned reloads and upgrades
  • Failover events

Other platforms for CVE-2026-76418

Microsoft Sentinel (KQL) Splunk (SPL) Elastic Security (Elastic) Sumo Logic CSE (Sumo) Google Chronicle (YARA-L) CrowdStrike LogScale (LogScale) All platforms (combined) →

Testing Methodology

Validate this detection against 1 adversary technique 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 further down this page.

  1. Test 1 Emit a stand-in firewall restart message to syslog (lab)

    Expected signal: A syslog event containing %ASA-, traceback and System restart.

Last updated: Research depth: standard
References (3)

Response Playbook

Triage

  1. Confirm the device runs an affected ASA or FTD build and has Remote Access SSL VPN with secondary authentication on a tunnel group, per the Cisco advisory.
  2. Identify the device, the reload time, and any burst of unauthenticated WebVPN connections from one or a few external sources beforehand.
  3. Check whether the reload matches a planned change, upgrade or HA failover.

Containment

  1. Upgrade to a fixed ASA or FTD release listed in the Cisco advisory, and follow BOD 26-04 guidance.
  2. Until patched, restrict SSL VPN exposure to known source ranges or disable secondary authentication on exposed tunnel groups where policy permits.
  3. Rate-limit or block the offending sources at the upstream edge.

Evidence Collection

  1. Collect the crashinfo and traceback files from the device before further reloads.
  2. Export firewall syslog, VPN session logs and threat-detection output for the window around each reload.
  3. Preserve upstream proxy, load balancer and flow logs for the same sources.

Escalation Criteria

  • !Escalate to incident response on repeated unexplained reloads or when the VPN is unavailable.
  • !Escalate if reloads coincide with other KEV Cisco or edge-device alerts, which can indicate a chained attack.
  • !Escalate if both units of a failover pair go down together.

Investigation Guide

Forensic Artifacts

  • >ASA or FTD crashinfo and traceback files
  • >Firewall syslog around each reload
  • >VPN tunnel-group configuration showing secondary authentication

Tuning Guidance

Exploitation leaves little beyond a crash, so treat these rules as medium or low fidelity. Baseline planned reloads per device, suppress change-managed windows and HA failovers, and prioritise alerts where a burst of unauthenticated WebVPN connections from one source precedes the reload. Patching is the definitive fix.

Hunting Queries

Builds a daily per-firewall count of reload and traceback messages so unusual restarts stand out after the 2026-10-28 disclosure.

Hunting — KQL
kql 
// df00tech DF00-a7d89fc7d5 · https://df00tech.com/detections/CVE-2026-76418 · licence: https://df00tech.com/detections/licence
Syslog | where TimeGenerated > ago(14d) | where SyslogMessage has_any ("%ASA-", "%FTD-") | where SyslogMessage has_any ("Reload", "traceback", "System restart") | summarize Reloads = count() by Computer, bin(TimeGenerated, 1d) | order by Computer asc, TimeGenerated asc
Hunting — SPL
spl 
``` df00tech DF00-a7d89fc7d5 · https://df00tech.com/detections/CVE-2026-76418 · licence: https://df00tech.com/detections/licence ```
index=network ("%ASA-" OR "%FTD-") (reload OR traceback OR "System restart") earliest=-14d | timechart span=1d count by host

Atomic Red Team Tests

Test 1 Emit a stand-in firewall restart message to syslog (lab)
linux

Simulates the telemetry the log rules key on by writing an ASA-style restart message to the local syslog on a Linux lab host. This does not exploit the vulnerability. Run only on a lab host.

Command

bash 
logger -t asa "%ASA-1-199010: Signal 11 received, System restart traceback test"

Cleanup

bash 
echo "no cleanup required"

Expected Telemetry

A syslog event containing %ASA-, traceback and System restart.

Expected Detection

The KQL, SPL and Sumo rules match on the message text; this test exercises the field mapping only.

Related Detections

Tactic Hub

TA0040 Impact ATT&CK Matrix

Related Techniques

T1499 Endpoint Denial of Service T1190 Exploit Public-Facing Application T1133 External Remote Services

Same Tactic: Impact

Popular Detections