CVE-2023-0440Public exploitNetwork attack vector

Email enumeration via divergent account responses

Published Jan 23, 2023 · Updated Apr 3, 2025

Observable response discrepancy in Healthchecks before 2.6 allows remote attackers to enumerate registered email addresses. The login and signup forms returned distinct validation messages after database lookups found an unknown or already registered email address. Unauthenticated network access to either form is sufficient, and the disclosed fact is limited to whether an account exists for the submitted address.

CVSS severity5.3
Medium
EPSS probability0.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Observable response discrepancy in Healthchecks before 2.6 allows remote attackers to enumerate registered email addresses. The login and signup forms returned distinct validation messages after database lookups found an unknown or already registered email address. Unauthenticated network access to either form is sufficient, and the disclosed fact is limited to whether an account exists for the submitted address.

The record

CVE
CVE-2023-0440
Published
Jan 23, 2023
Updated
Apr 3, 2025
Vendor
Healthchecks.io
Product
Healthchecks
Classifications
CWE-203, T1589.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 23, 2023CVE publishedPublication date reported by the CVE source.
  2. Apr 3, 2025Record 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=unspecified <v2.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Healthchecks.io · Healthchecksversion=unspecified <v2.6

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
5.3huntr.devCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-203Observable Discrepancy
T1589.002Email Addresses

Public exploit references

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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