What’s Vulnerable › Vulnerabilities

CVE-2021-40126: Cisco Umbrella Email Enumeration Vulnerability

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-11-04 · updated 2026-06-17
• Weakness: CWE-210

Description

A vulnerability in the web-based dashboard of Cisco Umbrella could allow an authenticated, remote attacker to perform an email enumeration attack against the Umbrella infrastructure. This vulnerability is due to an overly descriptive error message on the dashboard that appears when a user attempts to modify their email address when the new address already exists in the system. An attacker could exploit this vulnerability by attempting to modify the user's email address. A successful exploit could allow the attacker to enumerate email addresses of users in the system.

Affected products

• Cisco Umbrella Insights Virtual Appliance: all versions

References

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-umbrella-user-enum-S7XfJwDE
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-umbrella-user-enum-S7XfJwDE

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