CVE-2021-40126

MEDIUMNVD 4.34.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.3 under NVD CVSS v3. EPSS exploit probability: 0.8%, top 46% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
4.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 4.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
4.3
EG Score
4.3(medium)
EG Risk
—
EPSS
54.2%
KEV
Not listed

Published

November 4, 2021

Last Modified

November 21, 2024

References (2)

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 103 total refreshes for this CVE.

  1. 2026-07-22 22:50 UTCEG score recompute
  2. 2026-07-22 14:06 UTCEPSS rescore
  3. 2026-07-21 15:22 UTCEPSS rescore
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  73. 2026-05-26 13:42 UTCEPSS rescore
  74. 2026-05-26 08:02 UTCEG score recompute
  75. 2026-05-26 08:02 UTCGHSA enrichment

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Frequently asked(5)

What is CVE-2021-40126?
CVE-2021-40126 is a medium vulnerability published on November 4, 2021. 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…
When was CVE-2021-40126 disclosed?
CVE-2021-40126 was first published in the National Vulnerability Database on November 4, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-40126 actively exploited?
CVE-2021-40126 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 54.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-40126?
CVE-2021-40126 has a CVSS v3 base score of 4.3 (NVD).
How do I remediate CVE-2021-40126?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-40126, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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