CVE-2023-28623Network attack vector

Unauthorized account creation via unchecked authentication path

Published May 19, 2023 · Updated Feb 12, 2025

Improper authorization in Zulip 2.1.0 through 6.1 allows remote attackers to register accounts with email addresses absent from LDAP. The accounts_register view treats the presence of an external authentication method as permission to continue after LDAP lookup failure, without verifying that signup used that method. Exposure requires LDAP plus another external backend, no email backend, and an organization that permits joining without invitations; registration grants unauthorized organization access.

CVSS severity7.5
High
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authorization in Zulip 2.1.0 through 6.1 allows remote attackers to register accounts with email addresses absent from LDAP. The accounts_register view treats the presence of an external authentication method as permission to continue after LDAP lookup failure, without verifying that signup used that method. Exposure requires LDAP plus another external backend, no email backend, and an organization that permits joining without invitations; registration grants unauthorized organization access.

The record

CVE
CVE-2023-28623
Published
May 19, 2023
Updated
Feb 12, 2025
Vendor
Zulip
Product
Zulip
Classifications
CWE-862, CWE-285, T1136
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 19, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 12, 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=>= 2.1.0, < 6.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zulip · Zulipversion=>= 2.1.0, < 6.2

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
3.7NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-862Missing Authorization
CWE-285Improper Authorization
T1136Create Account

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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