CVE Identifiers (a.k.a. CVE IDs) are used to uniquely identifier a particular vulnerability. We've all seen them on various bulletins, and they're useful when researching an issue. But how are they assigned? What process is involved in getting a CVE ID for a bug, and how does the vendor fit in with that process? Can anyone ask for a CVE ID on a whim, or is some evidence or detail required?
There are multiple ways to obtain a CVE.
One could contact one of the CVE Numbering Authorities (CNA), an emergency response team (think CERT) or the CVE project. If the vendor of a product is listed as a CNA you must contact the vendor to obtain a CVE.
Sufficient information must be provided to allow the CVE assigner to take a decision (provide the CVE, merge with other CVEs etc).
For more information see http://cve.mitre.org/cve/request_id.html and http://cve.mitre.org/cve/cna.html#researcher_responsibilities
Some vendors such as Drupal will request CVE identifiers in bulk via openwall for published security announcements that do not already have a CVE requested by the researcher.