CVE-2016-4657
CVE-2016-4657 is a security flaw in Apple iOS, the operating system on iPhones and iPads. Attackers can run their own code on Apple iOS. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 24 May 2022.[1]
Apple iOS is in things households have, such as phones, computers, browsers and everyday apps, so the fix matters at home as much as at work. Apple has published a fix or advice.
Description
CISA calls it a webkit memory corruption in Apple iOS. In its words: “Apple iOS WebKit contains a memory corruption vulnerability that allows attackers to execute remote code or cause a denial-of-service (DoS) via a crafted web site. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and non-Apple products which rely on WebKit for HTML processing.”[1]
The underlying weakness is memory buffer error (CWE-119), in MITRE’s list of common software weaknesses.[2]
It scores 8.8 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Apple’s advisory has them[3]. CISA names the product as Apple iOS.
Every device with Apple iOS needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 24 May 2022, 2,098 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 14 Jun 2022 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 67%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Apple has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Update Apple iOS now.On iPhone and iPad: Settings, General, Software Update. On a Mac: System Settings, General, Software Update. Install it on every Apple device in the house. Then turn on automatic updates, so the next fix arrives on its own.
- If there’s no update, stop using it.CISA’s advice when a flaw being used in attacks has no fix is to stop using the product until it does.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 8.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 67%.[4] |
See also
Other Apple iOS flaws
- CVE-2022-42856: type confusion ·
- CVE-2016-4656: memory corruption ·
- CVE-2016-4655: information disclosure ·
- CVE-2019-7287: memory corruption ·
- CVE-2021-30762: webKit use-after-free ·
- CVE-2021-30761: webKit memory corruption ·
Other Apple flaws
- CVE-2026-86950, Apple devices: out-of-bounds write ·
- CVE-2026-65400, Apple macOS: improper authentication ·
- CVE-2025-43520, Apple devices: classic buffer overflow ·
- CVE-2025-43510, Apple devices: improper locking ·
- CVE-2025-31277, Apple devices: buffer overflow ·
Other memory buffer error flaws
- CVE-2026-88779, Citrix NetScaler: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88772, Citrix NetScaler: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88771, Citrix NetScaler: improper input validation ·
- CVE-2026-8452, Citrix NetScaler ADC and NetScaler Gateway: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2009-3459, Adobe Acrobat and Reader: heap-based buffer overflow ·
Added the same day
- CVE-2018-8611, Microsoft Windows: kernel privilege escalation ·
- CVE-2018-19953, QNAP Network Attached Storage (NAS): NAS file station cross-site scripting ·
- CVE-2018-19949, QNAP Network Attached Storage (NAS): NAS file station command injection ·
- CVE-2018-19943, QNAP Network Attached Storage (NAS): NAS file station cross-site scripting ·
- CVE-2017-8543, Microsoft Windows: search remote code execution ·
Every Apple flaw on CISA’s list · Everything added in May 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “Apple iOS Webkit Memory Corruption Vulnerability”. Known Exploited Vulnerabilities Catalog, added 24 May 2022.
- ^ National Institute of Standards and Technology. “CVE-2016-4657 Detail”. National Vulnerability Database, published 25 Aug 2016.
- ^ Apple. Advisories and fixes: support.apple.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.668, percentile 99.3, 31 Oct 2026.
- CVE Program. “CVE-2016-4657”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.