CVE-2021-40126Network attack vector

Email enumeration via descriptive address-conflict error

Published Nov 4, 2021 · Updated Nov 7, 2024

Information disclosure in the Cisco Umbrella web dashboard allows remote authenticated users to enumerate account email addresses. When an email-address change specifies an address assigned to another account, the dashboard returns an overly descriptive conflict error. A valid Umbrella account is required, and the response reveals whether each tested address belongs to a user without exposing other account data.

CVSS severity4.3
Medium
EPSS probability0.87%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in the Cisco Umbrella web dashboard allows remote authenticated users to enumerate account email addresses. When an email-address change specifies an address assigned to another account, the dashboard returns an overly descriptive conflict error. A valid Umbrella account is required, and the response reveals whether each tested address belongs to a user without exposing other account data.

The record

CVE
CVE-2021-40126
Published
Nov 4, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco Umbrella Insights Virtual Appliance
Classifications
CWE-210, T1087
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 4, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

ClamAV · Cisco Umbrella Insights Virtual Applianceversion=n/a

Published CVSS scores

4.3Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N/E:X/RL:X/RC:X

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-210Self-generated Error Message Containing Sensitive Information
T1087Account Discovery

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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