Detect Cisco Catalyst SD-WAN Manager Improper Output Encoding Exploitation in Splunk
Detects exploitation attempts targeting CVE-2026-20245, an improper encoding or escaping of output vulnerability (CWE-116) in Cisco Catalyst SD-WAN Manager. This vulnerability is actively exploited in the wild (CISA KEV) and may allow attackers to perform privilege escalation or inject malicious content through improperly encoded output. Detection focuses on anomalous authentication patterns, unexpected privilege changes, API abuse, and suspicious management plane activity against SD-WAN Manager instances.
MITRE ATT&CK
SPL Detection Query
index=network_security OR index=cisco_sdwan OR index=syslog
(sourcetype="cisco:sdwan" OR sourcetype="cisco:ios" OR sourcetype="syslog" OR sourcetype="cisco:asa")
(host="*vmanage*" OR host="*sdwan*manager*" OR host="*sdwanmgr*" OR vendor="Cisco")
earliest=-24h
| eval suspicious_indicator=case(
match(lower(_raw), "privilege.escal"), "PrivilegeEscalation",
match(lower(_raw), "inject|encod.*error|escape.*fail"), "OutputEncodingAbuse",
match(lower(_raw), "unauthorized.*admin|admin.*unauthorized"), "UnauthorizedAdminAccess",
match(lower(_raw), "/dataservice/.*403|/dataservice/.*401"), "APIAuthFailure",
true(), "Other"
)
| where suspicious_indicator!="Other"
| stats count as event_count, earliest(_time) as first_seen, latest(_time) as last_seen, values(_raw) as raw_events by host, suspicious_indicator, sourcetype
| where event_count >= 2
| eval first_seen=strftime(first_seen, "%Y-%m-%d %H:%M:%S"), last_seen=strftime(last_seen, "%Y-%m-%d %H:%M:%S")
| sort - event_count
| table first_seen, last_seen, host, sourcetype, suspicious_indicator, event_count, raw_eventsSearches Cisco SD-WAN Manager logs across Splunk indexes for privilege escalation attempts, output encoding errors, unauthorized admin access, and API authentication failures consistent with CVE-2026-20245 exploitation.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Legitimate administrative sessions generating privilege-related log entries during maintenance windows
- SD-WAN Manager version upgrades producing transient encoding or API error messages
- Automated configuration management tools repeatedly hitting management API endpoints
- Security assessment or compliance scanning tools triggering API auth failures
Other platforms for CVE-2026-20245
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 1SD-WAN Manager REST API Endpoint Enumeration and Auth Probe
Expected signal: Web server access logs and SD-WAN Manager audit logs should record multiple 401/403 responses to /dataservice/ endpoints from the probe source IP within a short time window
- Test 2Simulate Output Encoding Bypass via Crafted API Payload
Expected signal: SD-WAN Manager application logs should record the API request with the encoded payload; web access logs capture the POST to /dataservice/users with unexpected encoded characters in request body
- Test 3Post-Exploitation Privilege Escalation Simulation via vManage Admin API
Expected signal: SD-WAN Manager audit logs should record the group membership change attempt; if successful, an entry will appear under Administration > Audit Log showing the privilege modification with source IP and timestamp
Unlock Pro Content
Get the full detection package for CVE-2026-20245 including response playbook, investigation guide, and atomic red team tests.