Red Hat / Dogtag Certificate System did not prevent re-use of the one-time PIN used in the SCEP (Simple Certificate Enrollment Protocol) protocol enrollment requests. The check was done to ensure that PIN is valid, but the PIN was never removed from the list of valid PINs once it was used. An attacker possessing a valid SCEP enrollment one-time PIN could use it to generate an unlimited number of certificates.

Red Hat / Dogtag Certificate System's Certificate Authority can be asked to decrypt one-time PIN used in the SCEP (Simple Certificate Enrollment Protocol) protocol requests. This feature is intended to be used by Registration Authorities that act as proxies between CA users (e.g. network devices enrolling using SCEP protocol) and CA itself. However, Red Hat Certificate System lacked proper authentication mechanisms to ensure such decryption requests are only replied if sent form the configured Registration Authority. An attacker able to sniff SCEP request of the network could use this flaw to request decryption of the sniffed request and obtain one-time PIN.

Red Hat Certificate System updates add proper authentication, only configured authenticated Registration Authorities can request SCEP one-time PIN decryption.