Detect CVE-2026-55166: Lemur ACME SSRF and IDOR Leading to AWS IAM/PKI Compromise in IBM QRadar
Detects exploitation of CVE-2026-55166 in Netflix Lemur (versions < 1.9.2), which combines an ACME protocol Server-Side Request Forgery (CWE-918) with a creator-equality Insecure Direct Object Reference (CWE-639/CWE-285). Successful exploitation allows an attacker to pivot from certificate management to AWS IAM credential theft and PKI infrastructure compromise. PoC is publicly available.
MITRE ATT&CK
QRadar Detection Query
SELECT
sourceip,
"URL" as request_url,
username,
starttime,
CATEGORYDESCRIPTION(category) as event_category,
CASE
WHEN "URL" ILIKE '%169.254.169.254%' OR "URL" ILIKE '%fd00:ec2%' THEN 'CLOUD_METADATA_SSRF'
WHEN "URL" ILIKE '%acme%' AND "URL" ILIKE '%url=%' THEN 'ACME_CALLBACK_SSRF'
WHEN "URL" ILIKE '/api/v1/certificates/%' AND "METHOD" IN ('PUT','DELETE','GET') THEN 'IDOR_CERT_ACCESS'
ELSE 'SUSPICIOUS'
END as attack_phase,
COUNT(*) as event_count
FROM events
WHERE
devicetype IN (10, 15, 18, 105)
AND (
("URL" ILIKE '/api/v1/certificates%' OR "URL" ILIKE '/api/v1/authorities%' OR "URL" ILIKE '/api/v1/pending_certificates%')
AND (
"URL" ILIKE '%acme%'
OR "URL" ILIKE '%169.254.169.254%'
OR "URL" ILIKE '%challenge%'
OR ("URL" ILIKE '/api/v1/certificates/%' AND REGEXP_MATCH("URL", '/api/v1/certificates/[0-9]+'))
)
)
AND LOGSOURCETYPENAME(devicetype) NOT IN ('IBM Security AppScan', 'Tenable')
GROUP BY sourceip, "URL", username, starttime, event_category, attack_phase
HAVING COUNT(*) > 3
ORDER BY event_count DESC
LAST 1 HOURSQRadar AQL query correlating Lemur API access patterns consistent with SSRF exploitation via ACME callbacks and IDOR certificate enumeration, grouped by source IP and attack phase.
Data Sources
Required Tables
False Positives & Tuning
- Authorized vulnerability scanners (AppScan, Tenable) excluded via logsource filter
- ACME bot certificate renewals with legitimate callback URLs
- Bulk certificate operations by privileged service accounts
- Monitoring systems performing Lemur API health checks
Other platforms for CVE-2026-55166
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-2026-55166 ACME SSRF via HTTP-01 Challenge URL Injection
Expected signal: Outbound HTTP GET to 169.254.169.254 from Lemur process; web log entry for POST /api/v1/certificates with pluginOptions containing acme_challenge_url
- Test 2CVE-2026-55166 IDOR Certificate Enumeration via Sequential ID Access
Expected signal: 200 HTTP responses to GET /api/v1/certificates/[1-200] from a single source IP; Lemur audit log entries for cross-user certificate access
- Test 3CVE-2026-55166 Chained SSRF + IDOR for AWS IAM Credential Harvest
Expected signal: Sequential GET requests to /api/v1/authorities/[1-50]; POST to /api/v1/certificates with IMDS URL in pluginOptions; outbound TCP connection from Lemur process to 169.254.169.254:80
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Get the full detection package for CVE-2026-55166 including response playbook, investigation guide, and atomic red team tests.