Here’s a concise incident-style story based on that error message. The Case of the Too-Small Key
A mid-sized company was migrating its VPN remote access from an old Cisco ASA 5510 to a newer ASA 5508-X. The security team decided to renew the SSL certificate for the AnyConnect VPN endpoint, moving from a 1024-bit RSA certificate to a more secure 2048-bit one. The certificate was issued by their internal Microsoft CA. cisco asa certificate validation failed. ee key is too small
Let me clarify: On a Cisco ASA, when acting as an SSL/TLS server (e.g., for VPN), it validates client certificates if client cert auth is enabled. The error “EE key is too small” means a client presented a certificate whose public key size was below the ASA’s configured minimum (default often 1024 or 2048 depending on version/configuration). But in their case, no client cert auth was enabled. Here’s a concise incident-style story based on that
The ASA, when building the chain, used the older intermediate CA cert because it had a matching issuer name. It then checked the —but in the ASA’s validation logic, “EE key” in this context meant the public key of the end entity certificate presented by the client ? No, actually the error is misleading: it refers to the server certificate’s own key being too small ? Wait, not exactly. The certificate was issued by their internal Microsoft CA
One Monday morning, users started reporting that their AnyConnect VPN connections were failing. The ASA logs showed: certificate validation failed. ee key is too small The IT team was puzzled—they had just installed a brand-new 2048-bit certificate. Why would the ASA reject it as “too small”?
Upon investigation, the team found that the certificate chain installed on the ASA was incomplete. The ASA had the new server certificate (2048-bit) but still referenced an old, cached intermediate CA certificate that contained a 1024-bit public key.