Detect CVE-2026-48558 — SimpleHelp Authentication Bypass (CWE-347) in Google Chronicle
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
YARA-L Detection Query
rule cve_2026_48558_simplehelp_auth_bypass {
meta:
author = "df00tech Detection Platform"
description = "Detects exploitation of CVE-2026-48558 SimpleHelp authentication bypass via unauthenticated access to privileged endpoints"
severity = "CRITICAL"
priority = "HIGH"
reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-48558"
tactic = "TA0001"
technique = "T1190"
events:
$http.metadata.event_type = "NETWORK_HTTP"
$http.network.http.method = /GET|POST/
$http.network.http.response_code = /200|302/
$http.network.http.request_url = /\/admin|\/operator|\/technician|\/api\/admin/
not $http.principal.user.userid = /.+/
$http.target.port = /80|443|5850|5900/
condition:
$http
}Chronicle YARA-L 2.0 rule detecting unauthenticated HTTP requests to SimpleHelp administrative paths that return successful status codes, indicating authentication bypass exploitation of CVE-2026-48558.
Data Sources
Required Tables
False Positives & Tuning
- Chronicle log ingestion gaps where user context is not populated for legitimate authenticated sessions
- Internal SimpleHelp deployments with relaxed authentication on specific admin paths
- Automated IT operations tools performing unauthenticated health checks against SimpleHelp
- Misconfigured reverse proxies stripping authentication context before Chronicle ingestion
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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