Detect CoreWCF SAML Token Signature Validation Authentication Bypass (CVE-2026-54782) in IBM QRadar
CVE-2026-54782 is a critical (CVSS 10.0) authentication bypass vulnerability in CoreWCF.Primitives affecting SAML 1.1 and 2.0 token signature validation. An unauthenticated attacker can craft a SAML assertion with an invalid or missing signature that CoreWCF accepts as valid, bypassing all authentication controls on WCF service endpoints. Affects CoreWCF.Primitives < 1.8.1 and >= 1.9.0, < 1.9.1. A public PoC exists.
MITRE ATT&CK
QRadar Detection Query
SELECT
DATEFORMAT(starttime, 'YYYY-MM-dd HH:mm:ss') AS event_time,
sourceip,
username,
QIDNAME(qid) AS event_name,
logsourcename(logsourceid) AS log_source,
"URL" AS request_url,
magnitude,
UTF8(payload) AS raw_event
FROM events
WHERE
LOGSOURCETYPENAME(devicetype) IN ('Microsoft IIS', 'Microsoft Windows Security Event Log', 'Microsoft .NET')
AND (
LOWER(UTF8(payload)) LIKE '%corewcf%'
OR LOWER(UTF8(payload)) LIKE '%saml%'
OR LOWER(UTF8(payload)) LIKE '%wstrust%'
OR LOWER(UTF8(payload)) LIKE '%assertion%'
)
AND (
LOWER(UTF8(payload)) LIKE '%signature%invalid%'
OR LOWER(UTF8(payload)) LIKE '%bypass%auth%'
OR LOWER(UTF8(payload)) LIKE '%unsigned%token%'
OR LOWER(UTF8(payload)) LIKE '%securitytokenvalidation%'
)
AND starttime > NOW() - 86400000
ORDER BY starttime DESC
LIMIT 500QRadar AQL query correlating IIS, Windows Security, and .NET log sources for CoreWCF SAML signature validation anomalies indicative of CVE-2026-54782 exploitation attempts.
Data Sources
Required Tables
False Positives & Tuning
- SAML federation configuration changes causing transient validation exceptions
- Security scanning tools actively probing WCF endpoints
- Misconfigured identity providers sending malformed assertions during initial SSO setup
Other platforms for CVE-2026-54782
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 1Send Unsigned SAML 2.0 Assertion to CoreWCF Endpoint
Expected signal: IIS logs show POST /Service with HTTP 200 response; Windows Application Event Log shows no SecurityTokenValidationException; network capture shows SAML assertion without Signature element accepted
- Test 2Send Stripped Signature SAML 1.1 Token to CoreWCF wsHttpBinding Endpoint
Expected signal: Network capture shows WS-Security SOAP header with SAML 1.1 assertion lacking Signature; IIS or Kestrel logs show HTTP 200; no authentication failure event in Windows Security log
- Test 3Deploy Vulnerable CoreWCF Version and Validate Authentication Bypass via PoC
Expected signal: dotnet process spawned on port 5050; curl returns echo response without authentication challenge on 1.8.0; after patching to 1.8.1 the same request returns 401 or SOAP fault
Unlock Pro Content
Get the full detection package for CVE-2026-54782 including response playbook, investigation guide, and atomic red team tests.