Cyber Resilience

CVE-2016-4657

Memory Safety in Apple Iphone Os ≤ 9.3.5

CISA KEVActive ExploitationEUVD ExploitedPublic PoCMemory Safety
Published
25 August 2016
Modified
21 April 2026
KEV Added
24 May 2022
Patch / 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 0.64 99.1th percentile
Risk Priority 90 floored blend · peak EPSS

Summary

CVE-2016-4657 is a high-severity Out-of-bounds Write (CWE-787) vulnerability in Apple Iphone Os. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 0.9% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.

Deeper analysis AI-assisted summary

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

WebKit, the browser rendering engine in Apple iOS versions prior to 9.3.5, contains a memory corruption vulnerability tracked as CVE-2016-4657 and assigned CWE-787. The flaw is reachable remotely and carries a CVSS 3.1 base score of 8.8, reflecting network attack vector, low complexity, no required privileges, and required user interaction, with high impact on confidentiality, integrity, and availability.

An unauthenticated remote attacker can exploit the issue by serving a specially crafted web page that triggers out-of-bounds memory access when rendered in Safari or any WebKit-based application. Successful exploitation permits arbitrary code execution in the context of the mobile Safari process or, alternatively, a denial-of-service crash.

Apple’s security advisory and the corresponding support document HT207107 state that the vulnerability is resolved in iOS 9.3.5; users are advised to install the update promptly. Public references also link the same WebKit flaw to the Trident exploit kit observed in targeted mobile surveillance campaigns.

EU & UK References

Vulnerability Data

WebKit in Apple iOS before 9.3.5 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted web site.

CWE(s)
KEV Date Added
24 May 2022

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
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.
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
T1211 Exploitation for Stealth Stealth
Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2021-30761Same product: Apple Iphone Osboth on KEV
CVE-2016-4656Same product: Apple Iphone Osboth on KEV
CVE-2019-7287Same product: Apple Iphone Osboth on KEV
CVE-2019-7286Same product: Apple Iphone Osboth on KEV
CVE-2022-42827Same product: Apple Iphone Osboth on KEV
CVE-2014-4404Same product: Apple Iphone Osboth on KEV
CVE-2022-22587Same product: Apple Iphone Osboth on KEV
CVE-2023-28206Same product: Apple Iphone Osboth on KEV
CVE-2020-9907Same product: Apple Iphone Osboth on KEV
CVE-2020-9818Same product: Apple Iphone Osboth on KEV

Affected Assets

apple
iphone os
≤ 9.3.5

Mitigating Controls

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.

addresses: CWE-787

Out-of-bounds writes that corrupt control flow or inject shellcode are rendered non-executable by the same memory protections.

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-development practices (static analysis, bounds checking, code review) are the primary means of preventing out-of-bounds writes.

ID.RA-01 partial match
prevents

Vulnerability scanning and recording can discover out-of-bounds write flaws so they can be remediated.

PR.PS-02 partial match
prevents

Patching or replacing vulnerable software directly eliminates known instances of this coding weakness.

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.

finds

Security testing in development and acceptance can detect and prevent out-of-bounds write defects.

prevents

Secure development life cycle mandates practices that prevent out-of-bounds writes.

prevents

Application security requirements can specify bounds-checking and safe memory handling.

prevents

Secure architecture and engineering principles reduce the likelihood of buffer overflows.

prevents

Secure coding directly addresses out-of-bounds writes through language choice and coding standards.

prevents

Change management can enforce review gates that catch unsafe memory operations before deployment.

References