CVE-2026-70667 Netflix CVE debrief

Who should care

Operators of Lemur instances, security teams responsible for certificate management, and teams that handle internal requests and monitoring should assess exposure, verify remediation, and monitor for unusual internal requests. These teams should also evaluate the need for compensating controls for certificate validation and review relevant monitoring, detection, and logs for exposed assets.

Why it matters

CVE-2026-70667 allows an attacker to induce blind internal requests via CRL or OCSP URL validation in Lemur's TLS certificate creation process. Operators of Lemur instances should assess exposure, verify remediation, and monitor for unusual internal requests.

• Verify exposure to vulnerable Lemur instances
• Assess internal request monitoring and logging capabilities
• Evaluate the need for compensating controls for certificate validation

Technical summary

The _validate_revocation_url function in lemur/certificates/verify.py was vulnerable to redirect attacks, allowing an attacker to induce blind internal requests. This issue is fixed in version 1.9.3, which disables redirects and pins validated addresses while preserving the correct Host value. The vulnerability has a CVSS score of 6.3 and a severity of MEDIUM. Operators of Lemur instances should assess exposure and verify remediation. The fix preserves the correct Host value while preventing redirect attacks. The CVE record and source references provide details on the vulnerability in Lemur's TLS certificate creation process.

Defensive priority

Operators of Lemur instances should assess exposure and verify remediation

Recommended defensive actions

• Verify Lemur instance exposure to vulnerable versions
• Check for and apply version 1.9.3 or later upgrade
• Monitor for unusual internal requests via CRL or OCSP URLs
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and source references provide details on the vulnerability in Lemur's TLS certificate creation process. The issue allows for blind internal requests via CRL or OCSP URL validation. Operators should verify exposure to vulnerable Lemur instances, check for and apply version 1.9.3 or later upgrade, and monitor for unusual internal requests. The fix disables redirects and pins validated addresses while preserving the correct Host value. This vulnerability has a CVSS score of 6.3 and a severity of MEDIUM.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.