A cross-site request forgery flaw was found in etcd 3.3.1 and earlier. An attacker can set up a website that tries to send a POST request to the etcd server and modify a key. Adding a key is done with PUT so it is theoretically safe (can't PUT from an HTML form or such) but POST allows creating in-order keys that an attacker can send.
{
"cwe_ids": [
"CWE-352"
],
"github_reviewed_at": "2021-05-12T18:17:42Z",
"github_reviewed": true,
"nvd_published_at": "2018-04-03T16:29:00Z",
"severity": "HIGH"
}