CVE-2025-34026 Sumo Logic CSE · Sumo

Detect Versa Concerto Improper Authentication (CVE-2025-34026) in Sumo Logic CSE

Detects exploitation attempts targeting CVE-2025-34026, an improper authentication vulnerability (CWE-288) in Versa Concerto SD-WAN orchestration platform. This vulnerability allows attackers to bypass authentication controls, potentially enabling unauthorized access to the Concerto management interface. Listed as a CISA KEV, indicating active exploitation in the wild.

MITRE ATT&CK

Tactic
Initial Access Privilege Escalation Lateral Movement

Sumo Detection Query

Sumo Logic CSE (Sumo)
sql 
_sourceCategory=network/web OR _sourceCategory=proxy OR _sourceCategory=firewall
| where %"cs-host" matches "*concerto*" or %"cs-host" matches "*versa*" or _sourceHost matches "*concerto*" or _sourceHost matches "*versa*"
| parse regex field=_raw "\"(?P<http_method>GET|POST|PUT|DELETE|PATCH|OPTIONS)\s+(?P<uri_path>/[^\s]+)"
| parse regex field=_raw "HTTP/[0-9\.]+\"\s+(?P<status_code>[0-9]{3})"
| parse regex field=_raw "user=(?P<username>[^\s&]+)" nodrop
| where uri_path matches "*/api/*" or uri_path matches "*/auth*" or uri_path matches "*/admin*" or uri_path matches "*/management*"
| where status_code = "200"
| where isBlank(username) or username = "-" or toLowerCase(username) = "anonymous"
| count by _sourceHost, src_ip, uri_path, http_method, status_code, username
| sort by _count desc
critical severity medium confidence

Sumo Logic query detecting unauthenticated successful access to protected Versa Concerto management endpoints. Parses web access logs to flag HTTP 200 responses to sensitive paths where no authenticated user is identified.

Data Sources

Sumo Logic Cloud SIEMWeb access logsProxy logs

Required Tables

_sourceCategory=network/web_sourceCategory=proxy

False Positives & Tuning

  • Load balancer or reverse proxy health checks that appear as anonymous requests
  • Token-authenticated API clients where user field is not reflected in access logs
  • Internal microservices communicating with Concerto API without user context
  • Authorized penetration testing activity against Versa infrastructure

Other platforms for CVE-2025-34026

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

Testing Methodology

Validate this detection against 4 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.

  1. Test 1Unauthenticated GET to Versa Concerto API Endpoint

    Expected signal: HTTP access log on Concerto server showing GET /api/v1/system/info with source IP of test host, status 200, and empty/anonymous username field. Network flow showing connection to port 443.

  2. Test 2Authentication Bypass Probe via Malformed Auth Header

    Expected signal: Series of HTTP requests to multiple protected paths logged on Concerto host. Network proxy logs showing path enumeration pattern from single source IP within short time window.

  3. Test 3Post-Authentication-Bypass Configuration Read

    Expected signal: HTTP GET to /api/v1/vnf/inventory logged with 200 response and response body size. DLP or data exfiltration alerts if JSON response contains sensitive topology data. Network flow showing data transfer volume.

  4. Test 4Concerto Admin User Creation via Unauthenticated API

    Expected signal: HTTP POST to /api/v1/users logged. Concerto audit log entry for user creation event. If successful, new user visible in Concerto user management interface.

Last updated: 2026-06-19 Research depth: standard
References (3)

Response Playbook

Triage

  1. Identify the source IP of the request and determine if it is internal, external, or from a known management range. Cross-reference against the organization's approved Versa Concerto administrator IP allowlist.
  2. Review the specific endpoint accessed (e.g., /api/, /admin/, /auth/) and the HTTP method used. Determine whether the response returned sensitive data, configuration details, or administrative capabilities.
  3. Check the Versa Concerto application logs for session tokens or cookies present in the request — a CWE-288 bypass may involve manipulating or omitting authentication tokens rather than brute-forcing credentials.
  4. Correlate the alert timestamp against known maintenance windows, authorized penetration tests, or vulnerability scans. Contact the Concerto platform owner to verify whether the access was legitimate.
  5. Determine if the source IP has made additional requests to other protected paths or performed lateral movement to other SD-WAN nodes after initial access.

Containment

  1. If exploitation is confirmed, immediately block the source IP at the perimeter firewall and on Versa Concerto's access control list. Rotate any API tokens or session secrets that may have been exposed.
  2. Take the affected Concerto management interface offline or restrict access to a VPN-only or allowlisted-IP-only configuration until a patch is applied. Notify all Concerto administrators to invalidate active sessions and re-authenticate after remediation.
  3. Apply the vendor patch from Versa Networks as referenced in the security bulletin (https://security-portal.versa-networks.com/emailbulletins/6830f94328defa375486ff2e) as the primary remediation. If patching is not immediately possible, implement WAF rules to block unauthenticated requests to protected Concerto API paths.

Evidence Collection

  1. Collect full HTTP access logs from the Versa Concerto server covering the 48 hours before and after the detected event, including request headers, response codes, URI paths, and source IPs. Preserve logs to immutable storage.
  2. Capture network packet captures (PCAP) for the source IP's connections to the Concerto host if network monitoring is in place. Export firewall and proxy logs for the same time window and preserve chain-of-custody documentation.
  3. Extract the Concerto audit trail for any configuration changes, new user creation, policy modifications, or SD-WAN route changes occurring in the window following the detected access event.

Escalation Criteria

  • !Escalate to Incident Response if the unauthorized access resulted in configuration changes to SD-WAN policies, new administrative user creation, or exfiltration of device credentials or network topology data.
  • !Escalate immediately if lateral movement is detected from the Concerto host to managed SD-WAN branch devices, or if the attacker pivoted to internal network segments via the orchestration platform's trust relationships.

Investigation Guide

Related Techniques

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Forensic Artifacts

  • >Versa Concerto HTTP access logs at the application and reverse proxy level showing request URI, source IP, response code, and username fields
  • >Concerto audit database or audit log file recording administrative actions, user logins, and configuration changes with timestamps
  • >Network flow records (NetFlow/IPFIX) showing connections to Concerto management ports (typically 443/8443) from unexpected source IPs
  • >OS-level auth logs on the Concerto host (/var/log/auth.log or equivalent) for any SSH or OS-level access following the web exploit
  • >Memory dump or process list from the Concerto host to identify any post-exploitation tooling dropped after initial access

Tuning Guidance

This detection relies on identifying successful (HTTP 200) responses to protected Versa Concerto paths without authenticated user context. False positive rate can be reduced by: (1) maintaining an IP allowlist of known Concerto administrator hosts and excluding them from alerting, (2) identifying API token patterns used by legitimate automation and filtering on the absence of user-agent strings associated with those tools, (3) baselining normal access patterns by hour and flagging deviations rather than all unauthenticated successes. Since no affected version list is publicly available for CVE-2025-34026, detection must rely on behavioral indicators rather than version-specific signatures. Increase confidence by correlating with Concerto audit log entries showing configuration changes after the detected access event.

Hunting Queries

Hunt for anomalous access volume or diverse source IPs successfully reaching Versa Concerto protected endpoints over the past 7 days. High request counts or multiple unique sources accessing admin paths are indicators of scanning or exploitation.

Hunting — KQL
kql 
CommonSecurityLog
| where TimeGenerated > ago(7d)
| where DeviceVendor has_any ("Versa", "Concerto") or DeviceName has_any ("concerto", "versa")
| where RequestURL has_any ("/api/", "/auth", "/admin", "/management")
| where EventOutcome == "Success" or sc_status == 200
| summarize AccessCount=count(), UniqueURIs=dcount(RequestURL), SourceIPs=make_set(SourceIP) by bin(TimeGenerated, 1h), RequestClientApplication, DeviceName
| where AccessCount > 10 or array_length(SourceIPs) > 3
| order by TimeGenerated desc
Hunting — SPL
spl 
index=network OR index=web earliest=-7d
| where match(host, "(?i)(concerto|versa)")
| where match(uri_path, "(?i)(/api/|/auth|/admin|/management)")
| where status=200
| bucket span=1h _time
| stats count AS access_count, dc(src_ip) AS unique_sources, values(uri_path) AS paths BY _time, host
| where access_count > 20 OR unique_sources > 5
| sort -access_count

Atomic Red Team Tests

Test 1 Unauthenticated GET to Versa Concerto API Endpoint
linux

Simulates CVE-2025-34026 authentication bypass by sending an unauthenticated HTTP GET request directly to a protected Concerto API endpoint, testing whether the application returns HTTP 200 without requiring credentials.

Command

bash 
curl -sk -o /tmp/concerto_api_response.txt -w "%{http_code}" -X GET https://CONCERTO_HOST:443/api/v1/system/info -H 'Accept: application/json' --max-time 10; cat /tmp/concerto_api_response.txt

Cleanup

bash 
rm -f /tmp/concerto_api_response.txt

Expected Telemetry

HTTP access log on Concerto server showing GET /api/v1/system/info with source IP of test host, status 200, and empty/anonymous username field. Network flow showing connection to port 443.

Expected Detection

Detection rule triggers on unauthenticated successful access to /api/ path on Concerto host

Test 2 Authentication Bypass Probe via Malformed Auth Header
linux

Tests CWE-288 authentication bypass by sending requests with a malformed or empty Authorization header to Concerto management endpoints, which may be accepted by a vulnerable implementation.

Command

bash 
for path in /api/ /auth/login /admin /management/dashboard; do echo "Testing $path:"; curl -sk -o /dev/null -w "Status: %{http_code}\n" -X GET "https://CONCERTO_HOST:443${path}" -H 'Authorization: ' -H 'Accept: application/json' --max-time 5; done

Cleanup

bash 
No cleanup required — no files written

Expected Telemetry

Series of HTTP requests to multiple protected paths logged on Concerto host. Network proxy logs showing path enumeration pattern from single source IP within short time window.

Expected Detection

SIEM alert on multiple protected path accesses from single IP; potential detection on empty Authorization header bypass pattern

Test 3 Post-Authentication-Bypass Configuration Read
linux

Simulates the post-exploitation phase following a successful CVE-2025-34026 authentication bypass, where an attacker reads SD-WAN configuration or network topology data from the Concerto orchestrator API.

Command

bash 
curl -sk -X GET https://CONCERTO_HOST:443/api/v1/vnf/inventory -H 'Accept: application/json' -H 'Content-Type: application/json' --max-time 15 -o /tmp/concerto_topology.json 2>&1; echo "Response saved. Line count: $(wc -l < /tmp/concerto_topology.json)"

Cleanup

bash 
rm -f /tmp/concerto_topology.json

Expected Telemetry

HTTP GET to /api/v1/vnf/inventory logged with 200 response and response body size. DLP or data exfiltration alerts if JSON response contains sensitive topology data. Network flow showing data transfer volume.

Expected Detection

Alert on unauthenticated access to inventory/topology API endpoint; potential DLP alert on sensitive configuration data in HTTP response

Test 4 Concerto Admin User Creation via Unauthenticated API
linux

Tests whether CVE-2025-34026 permits an attacker to create a persistent backdoor administrative account via the Concerto user management API without authentication, a critical post-exploitation step for maintaining access.

Command

bash 
curl -sk -X POST https://CONCERTO_HOST:443/api/v1/users -H 'Accept: application/json' -H 'Content-Type: application/json' -d '{"username":"atomic_test_user","password":"AtomicTest123!","role":"admin"}' -o /tmp/user_create_response.txt -w "HTTP Status: %{http_code}\n" --max-time 10; cat /tmp/user_create_response.txt

Cleanup

bash 
rm -f /tmp/user_create_response.txt; curl -sk -X DELETE https://CONCERTO_HOST:443/api/v1/users/atomic_test_user --max-time 10

Expected Telemetry

HTTP POST to /api/v1/users logged. Concerto audit log entry for user creation event. If successful, new user visible in Concerto user management interface.

Expected Detection

Alert on unauthenticated POST to /api/ path; Concerto audit alert on new admin user creation; SIEM correlation between auth bypass detection and account creation within short time window

Related Detections

Tactic Hubs

TA0001Initial AccessTA0004Privilege EscalationTA0008Lateral Movement

Related Techniques

T1190Exploit Public-Facing ApplicationT1078Valid AccountsT1021Remote ServicesT1556Modify Authentication Process

Same Tactic: Initial Access

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