Cyber Resilience

CVE-2021-30661

Memory Safety in Apple Iphone Os ≤ 12.5.3

CISA KEVActive ExploitationEUVD ExploitedMemory Safety
Published
08 September 2021
Modified
23 October 2025
KEV Added
03 November 2021
Patch / advisory
View advisory
CVSS Score v3.1 8.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS Score 0.045 91th percentile
Risk Priority 90 floored blend · peak EPSS

Summary

CVE-2021-30661 is a high-severity Use After Free (CWE-416) vulnerability in Apple Iphone Os. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked in the top 9% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

A use-after-free vulnerability, tracked as CVE-2021-30661 and assigned CWE-416, affects WebKit components in multiple Apple products. It is present in versions of Safari prior to 14.1, iOS prior to 12.5.3 and 14.5, iPadOS prior to 14.5, watchOS prior to 7.4, tvOS prior to 14.5, and macOS Big Sur prior to 11.3. The flaw stems from improper memory management when handling web content and carries a CVSS 3.1 base score of 8.8.

An attacker can exploit the issue by serving maliciously crafted web content to a victim. Successful exploitation grants arbitrary code execution in the context of the affected process, requiring only that the user interact with the content (network vector, no privileges needed, user interaction required).

Apple security advisories HT212317, HT212318, HT212323, HT212324, and HT212325 state that the vulnerability is resolved by improved memory management in the versions listed above and recommend that users install the corresponding updates.

Apple has stated that it is aware of reports indicating the issue may have been actively exploited in the wild.

EU & UK References

Vulnerability Data

A use after free issue was addressed with improved memory management. This issue is fixed in Safari 14.1, iOS 12.5.3, iOS 14.5 and iPadOS 14.5, watchOS 7.4, tvOS 14.5, macOS Big Sur 11.3. Processing maliciously crafted web content may lead…

more

to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

CWE(s)
CWE-416
KEV Date Added
03 November 2021

Related Threats

MITRE ATT&CK Enterprise Techniques

T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-43529Same product: Apple Ipadosboth on KEV
CVE-2025-24085Same product: Apple Ipadosboth on KEV
CVE-2023-28205Same product: Apple Ipadosboth on KEV
CVE-2023-43000Same product: Apple Ipadosboth on KEV
CVE-2022-22620Same product: Apple Ipadosboth on KEV
CVE-2023-41976Same product: Apple Ipados
CVE-2023-42950Same product: Apple Ipados
CVE-2023-40414Same product: Apple Ipados
CVE-2023-42970Same product: Apple Ipados
CVE-2019-8605Same product: Apple Iphone Osboth on KEV

Affected Assets

apple
safari
≤ 14.1
apple
ipados
≤ 14.5
apple
iphone os
≤ 12.5.3 · 14.0 — 14.5
apple
macos
11.0 — 11.3
apple
tvos
≤ 14.5
apple
watchos
≤ 7.4

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 3 hardening rules · 3 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V1.4.3

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SI-16 Memory Protection
addresses: CWE-416

Use-after-free exploits that achieve arbitrary code execution are blocked or significantly hardened by non-executable pages and ASLR.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly incorporate memory-safety tooling and reviews that prevent most use-after-free defects.

ID.RA-01 partial match
prevents

Vulnerability identification processes can discover use-after-free issues via scanning or analysis but do not prevent their introduction.

PR.PS-02 partial match
prevents

Routine patching removes known use-after-free instances after they have been introduced in released software.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development can detect use-after-free bugs before release.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC mandates memory-safety practices that reduce use-after-free defects.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify memory-management rules that mitigate use-after-free.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles include memory-safety design choices that limit use-after-free exposure.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prescribe avoidance of use-after-free patterns.

A.8.32 Change management partial match
prevents

Change-management processes help ensure memory-safety fixes are deployed consistently.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 8 (1 rule)
  • V-248592 OL 8 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416
RHEL 8 (1 rule)
  • V-230279 RHEL 8 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416
RHEL 9 (1 rule)
  • V-257794 RHEL 9 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416

References