CVE-2021-30737Public exploitNetwork attack vector

Code execution via ASN.1 bit-string heap overflow

Published Sep 8, 2021 · Updated Aug 3, 2024

Memory corruption in Apple's ASN.1 decoder allows remote attackers to execute code on iOS, iPadOS, and macOS via a crafted certificate. In sec_asn1d_parse_bit_string, a one-byte child clears the shared output pointer, enabling a small reallocation before later child bytes are copied beyond it. A target process must parse the certificate, and successful exploitation runs attacker-controlled code in that process.

CVSS severity8.8
High
EPSS probability1.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Apple's ASN.1 decoder allows remote attackers to execute code on iOS, iPadOS, and macOS via a crafted certificate. In sec_asn1d_parse_bit_string, a one-byte child clears the shared output pointer, enabling a small reallocation before later child bytes are copied beyond it. A target process must parse the certificate, and successful exploitation runs attacker-controlled code in that process.

The record

CVE
CVE-2021-30737
Published
Sep 8, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
iOS and iPadOS
Classifications
CWE-787, T1203
Attack vector
network
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 <14.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Apple · iOS and iPadOSversion=unspecified <14.6
Apple · macOSversion=unspecified <11.4; version=unspecified <12.5; version=unspecified <14.6; version=unspecified <2021; version=unspecified <7.5

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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.

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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 exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

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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