CVE-2026-70667 Lemur: SSRF protection in certificate revocation checking bypassable via HTTP redirects and DNS rebinding (incomplete fix for GHSA-54vg-pfh7-jq95)
Attackers can bypass SSRF protections in Lemur's certificate revocation checks via redirects and DNS rebinding to access internal resources.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-70667?
CVE-2026-70667 is a medium-severity server-side request forgery vulnerability in Netflix lemur, published on 18 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-70667?
3 open source packages ship an affected version, including lemur.
| Package | Affected | Fixed in |
|---|---|---|
lemur PyPI | All versions | 1.9.3 |
lemur PyPI | All versions | 1.9.3 |
lemur PyPI | All versions | 1.9.3 |
How do I fix CVE-2026-70667?
Upgrade lemur to 1.9.3 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-70667 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-70667 exists.
Sources
Also known as GHSA-f3qq-49m6-rw8f, PYSEC-2026-3676.