CVE-2021-1883

Heap corruption via malicious server messages

Published Sep 8, 2021 · Updated Aug 3, 2024

Heap corruption in Heimdal across affected Apple operating systems allows attackers to corrupt heap memory via crafted server messages. Apple states only that improved checks address the flaw and has not disclosed the parser, message field, or incorrect operation involved. Reachability requires processing a malicious server response; the published record establishes heap corruption but does not claim code execution or service interruption.

CVSS severity5.5
Medium
EPSS probability2.00%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap corruption in Heimdal across affected Apple operating systems allows attackers to corrupt heap memory via crafted server messages. Apple states only that improved checks address the flaw and has not disclosed the parser, message field, or incorrect operation involved. Reachability requires processing a malicious server response; the published record establishes heap corruption but does not claim code execution or service interruption.

The record

CVE
CVE-2021-1883
Published
Sep 8, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
iOS and iPadOS
Classifications
CWE-787
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 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 <14.5

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Apple · iOS and iPadOSversion=unspecified <14.5
Apple · tvOSversion=unspecified <14.5
Apple · macOSversion=unspecified <11.3; version=unspecified <2021
Apple · watchOSversion=unspecified <7.4

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write

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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