CVE-2026-71417 Lemur: Any user can revoke arbitrary certificates at the CA by uploading a duplicate record and revoking it
An attacker can revoke arbitrary TLS certificates by uploading duplicates, causing fleet-wide denial of service in Lemur.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-71417?
CVE-2026-71417 is a high-severity missing authorization vulnerability in Netflix lemur, published on 18 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Lemur manages TLS certificate creation. Prior to 1.9.3, POST /api/1/certificates/upload allowed a non-read-only user to create a duplicate row using another certificate body, authority_id, serial, or external_id without requiring permission on the underlying authority. PUT /api/1/certificates//revoke authorized the caller against only the selected Lemur row, so the creator of the duplicate bypassed CertificatePermission. The duplicate had no cert.endpoints, which also bypassed the safeguard that prevents revocation of deployed certificates. Issuer plugins then revoked the real CA-side certificate using certificate.body or external_id under the stored authority credentials. An attacker could therefore revoke arbitrary managed certificates and cause fleet-wide TLS denial of service. The fix rejects duplicate authority_id and serial identities, requires authority access on upload, and checks every matching row during revocation. This issue is fixed in version 1.9.3.
Weakness: CWE-639
Which versions are affected by CVE-2026-71417?
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-2026-71417?
Upgrade lemur to 1.9.3 or later.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-71417 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-71417 exists.
Sources
Also known as GHSA-pxmc-2ffp-8j67, PYSEC-2026-3678.