CVE-2021-47971Public exploit

Application crash via oversized note contents

Published May 16, 2026 · Updated May 16, 2026

Denial of service in version 5.3 of the affected iOS notes application allows attackers to trigger a crash by pasting oversized text. The note editor accepts a 350,000-character string twice and then stops working; public sources do not identify the precise allocation or buffer operation. Exploitation requires opening the app, creating a note, generating the text payload, and pasting the payload twice on the device.

CVSS severity8.7
High
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in version 5.3 of the affected iOS notes application allows attackers to trigger a crash by pasting oversized text. The note editor accepts a 350,000-character string twice and then stops working; public sources do not identify the precise allocation or buffer operation. Exploitation requires opening the app, creating a note, generating the text payload, and pasting the payload twice on the device.

The record

CVE
CVE-2021-47971
Published
May 16, 2026
Updated
May 16, 2026
Vendor
Zhejiang Zoneland Zongheng Network Technology Co., Ltd.
Product
My Notes Safe
Classifications
CWE-789, T1499.004
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. May 16, 2026CVE publishedPublication date reported by the CVE source.
  2. May 16, 2026Record 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=5.3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Zhejiang Zoneland Zongheng Network Technology Co., Ltd. · My Notes Safeversion=5.3

Published CVSS scores

7.5VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA: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)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-789Memory Allocation with Excessive Size Value
T1499.004Application or System Exploitation

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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