What is CVE-2020-9818?

CVE-2020-9818 is a high-severity vulnerability in Apple iOS, classified under Out-of-bounds Write. CVSS score: 8.8/10. Published 2020-06-09.

How severe is CVE-2020-9818?

High severity. CVSS v3 base score is 8.8 out of 10.

Is CVE-2020-9818 known to be exploited?

Yes. CVE-2020-9818 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating it is being actively exploited. 2 public proof-of-concept repositories are indexed.

Buffer overflow in Apple iOS

CVE-2020-9818

An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in iOS 13.5 and iPadOS 13.5, iOS 12.4.7, watchOS 6.2.5. Processing a maliciously crafted mail message may lead to unexpected memory modification or application termination.

Vulnerability class: Buffer Overflow

Published 2020-06-09 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.023 (82.9th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 83rd percentile — 82.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.023 · newest: 0.023 · change: 0.000

Affected products

Apple iOS — versions unspecified
Apple Ios-1 — versions unspecified
Apple Ipados
Apple Iphone OS
Apple watchOS — versions unspecified

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2021-11-03. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2022-05-03.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

support.apple.com/HT211168 (Release Notes, Vendor Advisory)
support.apple.com/HT211175 (Release Notes, Vendor Advisory)
support.apple.com/HT211169 (Release Notes, Vendor Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2020-9818?: CVE-2020-9818 is a high-severity vulnerability in Apple iOS, classified under Out-of-bounds Write. CVSS score: 8.8/10. Published 2020-06-09.
How severe is CVE-2020-9818?: High severity. CVSS v3 base score is 8.8 out of 10.
Is CVE-2020-9818 known to be exploited?: Yes. CVE-2020-9818 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating it is being actively exploited. 2 public proof-of-concept repositories are indexed.