A vulnerability in the web UI of Cisco Umbrella could allow an unauthenticated, remote attacker to negatively affect the performance of this service.
The vulnerability exists due to insufficient rate limiting controls in the web UI. An attacker could exploit this vulnerability by sending crafted HTTPS packets at a high and sustained rate. A successful exploit could allow the attacker to negatively affect the performance of the web UI.
Cisco has addressed this vulnerability.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-1350
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-umb-dos-dgKzDEBP