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Weekly Signal
Live intelligence Updated 20 Aug 2026 · 23:28 UTC

Apple · iOS, Iphone Os

CVE-2016-4657

Apple iOS Webkit Memory Corruption Vulnerability

Recommended action

Validate affected assets and exposure now, then remediate on an accelerated schedule. Apple Security release notes HT207107

View response plan
CVSS8.8
EPSS63.6%
KEVYes
ExploitationConfirmed exploitation
RemediationFixed release identified ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 63.6%; technical severity is CVSS 8.8.

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.

Who should care

  • Teams operating iOS, Iphone Os
  • Vulnerability and exposure management teams
  • Security operations teams monitoring exploitation activity

Response plan

What I would do

  1. Confirm whether iOS, Iphone Os is present in the environment.
  2. Identify affected versions and establish whether vulnerable services are exposed or reachable.
  3. Apple Security release notes HT207107
  4. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Treatment intelligence

Remediation intelligence

Not yet verified

Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.

Verification noteAutomated link verification has not completed for this guidance yet.

Technical details

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE
CWE-119
Affected versions
Apple iOS; Apple Iphone Os (End Excluding 9.3.5)
Fixed versions
Apple Iphone Os (Fixed from 9.3.5)
Published
25 August 2016
Attack vector
Network
Privileges required
None
User interaction
Required

Signal timeline

  1. CVE published
  2. Added to CISA KEV
  3. Latest EPSS score: 63.6%
  4. Signal calculated at 80

External references

Live public intelligence This assessment combines public-source evidence. Validate the affected product, version and exposure against your own environment before making a risk decision.