Lemur 1.9.0 and earlier versions have a combined vulnerability chain involving three independent flaws: (1) Lemur auto-provisions any new SSO identity as active without admin approval or restrictions, allowing any federated IdP user to become an active Lemur user; (2) the ACME authority creation endpoint accepts an attacker-controlled acme_url parameter and performs an unrestricted server-side HTTP fetch, enabling SSRF attacks to the AWS EC2 metadata service at 169.254.169.254, leaking AWS IAM credentials; (3) the certificate key-fetch endpoint grants unconditional access to the certificate's original creator regardless of ownership transfer, allowing persistent private key exfiltration. Together, these flaws enable a low-privilege SSO user to exfiltrate AWS STS credentials of the Lemur worker role and obtain permanent copies of TLS private keys issued by Lemur.

An attacker with any valid SSO session in the Lemur environment can escalate privileges to compromise AWS IAM credentials associated with the Lemur worker role and permanently access TLS private keys issued by Lemur. This leads to a complete compromise of AWS resources accessible by the worker role and undermines the confidentiality and integrity of TLS certificates managed by Lemur. The vulnerability chain bypasses normal authorization controls and ownership transfer mechanisms, resulting in persistent unauthorized access.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict SSO access to trusted users only and monitor for suspicious ACME authority creation requests. Consider disabling or restricting the ACME authority creation endpoint and reviewing certificate key access policies to limit exposure. Do not rely on ownership transfer to revoke creator access. Follow vendor advisories closely for updates and apply patches promptly once released.