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CVE-2021-30666

Apple iOS WebKit Buffer Overflow

8.8 HIGHActively exploited (CISA KEV)EPSS 3.00%
  1. Published8 Sept 2021
  2. Added to CISA KEV3 Nov 2021
  3. Remediation due17 Nov 2021
Actively exploited (CISA KEV)

Apple iOS WebKit contains a buffer-overflow vulnerability that leads to code execution when processing maliciously crafted web content. 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.

Added to KEV: 3 Nov 2021Federal remediation due: 17 Nov 2021

Description

A buffer overflow issue was addressed with improved memory handling. This issue is fixed in iOS 12.5.3. Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionRequired
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

Apple iPhone OS< 12.5.3

Remediation

Fixed in
Apple iPhone OS≥ 12.5.3

References

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Frequently asked

Is CVE-2021-30666 being actively exploited?

Yes. CVE-2021-30666 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 3 Nov 2021.

How severe is CVE-2021-30666?

CVE-2021-30666 has a CVSS 3.1 base score of 8.8, rated high. EPSS estimates a 3.00% probability of exploitation.

Which products are affected by CVE-2021-30666?

Affected products include Apple iPhone OS.

How do I fix CVE-2021-30666?

Upgrade affected software to a fixed version, for example Apple iPhone OS 12.5.3 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2021-30666 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.