CVE-2021-1771Network attack vector

Unauthorized iMessage group reentry

Published Apr 2, 2021 · Updated Aug 3, 2024

Authentication bypass in Apple macOS before 11.2 allows remote authenticated users to rejoin iMessage groups after removal. The Messages group-membership check fails to enforce removal state, so a previously removed participant can send or receive in the group again. An attacker needs a valid iMessage account and prior group membership; impact is unauthorized participation in the conversation, with no evidence of code execution or broad data disclosure.

CVSS severityUnavailable
Unscored
EPSS probability0.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Apple macOS before 11.2 allows remote authenticated users to rejoin iMessage groups after removal. The Messages group-membership check fails to enforce removal state, so a previously removed participant can send or receive in the group again. An attacker needs a valid iMessage account and prior group membership; impact is unauthorized participation in the conversation, with no evidence of code execution or broad data disclosure.

The record

CVE
CVE-2021-1771
Published
Apr 2, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
macOS
Classifications
Unavailable
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 2, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=unspecified <11.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Apple · macOSversion=unspecified <11.2

Published CVSS scores

No CVSS assessment is available in this record.

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

No sourced classifications are available.

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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