CVE-2020-3877Network attack vector

Remote code execution via AnnotationKit out-of-bounds read

Published Feb 27, 2020 · Updated Aug 4, 2024

Out-of-bounds read in Apple AnnotationKit in macOS before 10.15.3 and watchOS before 6.1.2 allows remote attackers to crash apps or execute code. HandwritingProvider fails to validate user-supplied handwriting data before reading past the end of an allocated buffer. On macOS, the target must open Messages and code execution requires chaining with another flaw; Apple has not published an equivalent watchOS gate.

CVSS severity7.5
High
EPSS probability2.05%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in Apple AnnotationKit in macOS before 10.15.3 and watchOS before 6.1.2 allows remote attackers to crash apps or execute code. HandwritingProvider fails to validate user-supplied handwriting data before reading past the end of an allocated buffer. On macOS, the target must open Messages and code execution requires chaining with another flaw; Apple has not published an equivalent watchOS gate.

The record

CVE
CVE-2020-3877
Published
Feb 27, 2020
Updated
Aug 4, 2024
Vendor
Apple
Product
macOS
Classifications
CWE-125, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 27, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 <macOS Catalina 10.15.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Apple · macOSversion=unspecified <macOS Catalina 10.15.3
Apple · watchOSversion=unspecified <watchOS 6.1.2

Published CVSS scores

7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:N/I:N/A:P

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1203Exploitation for Client Execution

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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