Detect Cisco Catalyst SD-WAN Controller and Manager Authentication Bypass (CVE-2026-20127) in CrowdStrike LogScale
CVE-2026-20127 is an authentication bypass vulnerability (CWE-287) affecting Cisco Catalyst SD-WAN Controller and Manager. A remote, unauthenticated attacker may exploit improper authentication mechanisms to gain unauthorized access to the management plane. This vulnerability is actively exploited in the wild per CISA KEV and is subject to Emergency Directive ED-26-03.
MITRE ATT&CK
LogScale Detection Query
#event_simpleName=NetworkConnectIP4 OR #event_simpleName=HttpRequest
| LocalAddressIP4 = /^(?:10\.|172\.(?:1[6-9]|2[0-9]|3[01])\.|192\.168\.)/
| (RemotePort in (443, 8443, 8080, 8888) OR RemotePort = 443)
| (HttpPath = /\/(?:dataservice|j_security_check|rest)\// OR HttpStatusCode in ("401", "403"))
| HostnameField = /(?i)(vmanage|vbond|vsmart|sdwan)/
| groupBy([RemoteAddressIP4, HostnameField, HttpPath], function=[count(aid, as=attempt_count), min(timestamp, as=first_seen), max(timestamp, as=last_seen), collect(HttpStatusCode, as=status_codes)])
| where attempt_count >= 3
| sort(attempt_count, order=desc)CrowdStrike Falcon LogScale CQL query identifying repeated network connections from internal sources to Cisco SD-WAN management hosts on common management ports, filtering for authentication failure response codes and sensitive API paths consistent with CVE-2026-20127 exploitation attempts.
Data Sources
Required Tables
False Positives & Tuning
- Falcon sensor telemetry from hosts with expired SD-WAN management credentials
- Automated infrastructure-as-code pipelines calling vManage APIs without refreshed tokens
- Authorized penetration testing activity against SD-WAN management interfaces
- Internal monitoring dashboards polling vManage health endpoints unauthenticated
Other platforms for CVE-2026-20127
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 1Unauthenticated vManage REST API Enumeration
Expected signal: Network logs showing repeated HTTP GET/POST requests to vManage management IP on port 443 with response codes 401, 403, or 200 from the test host IP across multiple /dataservice/ URI paths
- Test 2Authentication Bypass Session Token Harvesting Simulation
Expected signal: HTTP request to /dataservice/device with custom Cookie header not matching any active session, logged in vManage access log with source IP of test host; response will be 401 or 403 in a patched system, or 200 in a vulnerable one
- Test 3vManage Admin Account Creation via Bypass
Expected signal: vManage audit log entry for POST /dataservice/admin/user with actor IP matching test host; new user 'testbackdoor' visible in GET /dataservice/admin/user response; network logs showing POST request to admin/user endpoint
References (4)
- https://www.cisa.gov/news-events/directives/ed-26-03-mitigate-vulnerabilities-cisco-sd-wan-systems
- https://www.cisa.gov/news-events/directives/supplemental-direction-ed-26-03-hunt-and-hardening-guidance-cisco-sd-wan-systems
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sdwan-rpa-EHchtZk
- https://nvd.nist.gov/vuln/detail/CVE-2026-20127
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