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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-1098
• etcd-io/etcd#9353
• etcd-io/etcd@a7e5790
• https://bugzilla.redhat.com/show_bug.cgi?id=1552714
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JX7QTIT465BQGRGNCE74RATRQLKT2QE4/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UPGYHMSKDPW5GAMI7BEP3XQRVRLLBJKS/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JX7QTIT465BQGRGNCE74RATRQLKT2QE4/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UPGYHMSKDPW5GAMI7BEP3XQRVRLLBJKS/