Detect CVE-2026-48558 — SimpleHelp Authentication Bypass (CWE-347) in Microsoft Sentinel
Detects exploitation of CVE-2026-48558, an authentication bypass vulnerability in SimpleHelp remote support software caused by improper verification of cryptographic signatures (CWE-347). This KEV-listed vulnerability allows unauthenticated attackers to bypass authentication controls. SimpleHelp is commonly used by MSPs and IT support teams, making it a high-value target for initial access and lateral movement.
MITRE ATT&CK
KQL Detection Query
let SimpleHelpPorts = dynamic([80, 443, 5850, 5900]);
let SuspiciousAdminPaths = dynamic(["/admin", "/api/admin", "/operator", "/technician"]);
union DeviceNetworkEvents, CommonSecurityLog, W3CIISLog
| where TimeGenerated >= ago(7d)
| where (
(RemotePort in (SimpleHelpPorts) or DestinationPort in (SimpleHelpPorts))
or (csUriStem has_any (SuspiciousAdminPaths))
)
| where (
(csMethod in ("GET", "POST") and (csUriStem has "/admin" or csUriStem has "/operator"))
or (sc-status in (200, 302) and cs-username == "-" and csUriStem has_any (SuspiciousAdminPaths))
)
| extend AuthBypassIndicator = case(
sc-status == 200 and cs-username == "-" and csUriStem has_any (SuspiciousAdminPaths), "Unauthenticated access to admin endpoint",
sc-status == 302 and csUriStem has "/admin", "Redirect from admin path without auth session",
"Suspicious SimpleHelp request"
)
| project TimeGenerated, AuthBypassIndicator, csUriStem, sc-status, cs-username, c-ip, s-ip, csMethod, csUserAgent
| order by TimeGenerated descDetects unauthenticated access to SimpleHelp administrative and operator endpoints, indicative of authentication bypass exploitation of CVE-2026-48558. Looks for HTTP 200/302 responses to privileged paths without valid session credentials.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate SimpleHelp administrators accessing the panel from expected internal IP ranges
- Vulnerability scanners or asset management tools probing SimpleHelp service ports
- Load balancer health checks targeting SimpleHelp web endpoints
- Automated monitoring solutions that probe application availability endpoints
Other platforms for CVE-2026-48558
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 1CVE-2026-48558 — Unauthenticated Admin Endpoint Access Probe
Expected signal: Web server access logs will show GET requests to /admin, /operator, /technician, and /api/admin from the test host IP. Network flow data will show connections from test host to SimpleHelp port. IDS/IPS may generate HTTP policy violation alerts.
- Test 2CVE-2026-48558 — Signature Verification Bypass via Malformed Token
Expected signal: Application logs should show authentication attempts with malformed tokens. Web server logs will record requests with Authorization headers containing invalid credentials. Endpoint detection may flag the curl process making connections to internal services.
- Test 3CVE-2026-48558 — Post-Bypass Operator Account Enumeration
Expected signal: Multiple sequential API requests to /api/admin/* paths from single source IP within short timeframe. Application logs show operator/technician/config endpoint access. UEBA tools may flag unusual API access patterns if baselining is in place.
References (4)
- https://simple-help.com/security/simplehelp-security-update-2026-05
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
- https://nvd.nist.gov/vuln/detail/CVE-2026-48558
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