SSRF in Netflix Lemur

CVE-2026-70667

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.

Vulnerability class: TOCTOU (Time-of-Check to Time-of-Use)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 6.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.002 (6.8th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 6.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-70667: held from 0.001 to 0.002.

EPSS over last 30 days · oldest: 0.001 · newest: 0.002 · change: +0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-70667?
CVE-2026-70667 is a medium-severity vulnerability in Netflix Lemur, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 6.3/10. Published 2026-08-18.
How severe is CVE-2026-70667?
Medium severity. CVSS v3 base score is 6.3 out of 10.