CVE-2024-21630Network attack vector

Unauthorized stream subscriptions via unchecked reusable invitations

Published Jan 25, 2024 · Updated May 29, 2025

Missing authorization in Zulip Server 8.0 allows remote authenticated users to invite new users to streams they cannot otherwise add users to. The generate_multiuse_invite_backend API accepts stream_ids and creates a reusable invitation without checking can_subscribe_other_users(). Reachability requires a role that can create reusable invitations but cannot subscribe other users; invited users gain access only to streams visible to the inviter.

CVSS severity4.3
Medium
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authorization in Zulip Server 8.0 allows remote authenticated users to invite new users to streams they cannot otherwise add users to. The generate_multiuse_invite_backend API accepts stream_ids and creates a reusable invitation without checking can_subscribe_other_users(). Reachability requires a role that can create reusable invitations but cannot subscribe other users; invited users gain access only to streams visible to the inviter.

The record

CVE
CVE-2024-21630
Published
Jan 25, 2024
Updated
May 29, 2025
Vendor
Zulip
Product
Zulip
Classifications
CWE-862, T1136
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 25, 2024CVE publishedPublication date reported by the CVE source.
  2. May 29, 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== 8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Zulip · Zulipversion== 8.0

Published CVSS scores

4.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/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 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-862Missing 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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