CVE-2026-70667
MediumCVSS 6.3Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
Lemur before version 1.9.3 contains a vulnerability in _validate_revocation_url that does not properly validate URLs after HTTP redirects, allowing access to internal addresses (loopback, RFC1918, link-local, instance-metadata). Additionally, there is a time-of-check time-of-use window enabling DNS rebinding attacks. An operator uploading a certificate via POST /api/1/certificates/upload can trigger unwanted internal requests.
Risk Assessment
An attacker could exploit this to probe internal services and cause side effects from the Lemur host's network position, potentially leading to confidentiality and integrity breaches.
Recommendation
Upgrade Lemur to version 1.9.3 or later, which disables redirects and pins validated addresses.
Original NVD description (English source)
Lemur manages TLS certificate creation. Prior to 1.9.3, _validate_revocation_url in lemur/certificates/verify.py checked the original CRL or OCSP URL but the later request could reach a different destination. The CRL requests.get call followed HTTP redirects without validating each Location target, so a public attacker-controlled URL could redirect to loopback, RFC1918, link-local, or instance-metadata addresses. Validation and connection also performed separate DNS resolutions, creating a time-of-check time-of-use window for DNS rebinding on both CRL and OCSP paths. An operator uploading a certificate through POST /api/1/certificates/upload could therefore induce blind internal requests despite the earlier mitigation. The fix disables redirects and pins validated addresses while preserving the correct Host value. This issue is fixed in version 1.9.3.