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Fencer Intel
medium 4.3

CVE-2021-40126 json

Cisco Umbrella Email Enumeration Vulnerability

published 5y ago modified 4mo ago also EUVD-2021-27313

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 59%
public exploits
0
none known

Summary

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.

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2y ago

Exploit prediction

0.87% chance of exploitation in the next 30 days, higher than 59% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
NVD 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
NVD 2.0 4.0 AV:N/AC:L/Au:S/C:P/I:N/A:N

Affected products

  • Cisco Cisco Umbrella Insights Virtual Appliance

Classification

Weakness
  • CWE-210 Self-generated Error Message Containing Sensitive Information
  • CWE-209 Generation of Error Message Containing Sensitive Information

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.