CVE-2020-9818: in the CISA KEV catalogue
Apple iOS, iPadOS, and watchOS Out-of-Bounds Write Vulnerability. CISA added CVE-2020-9818 to the Known Exploited Vulnerabilities catalogue on 2021-11-03 with a default due date of 2022-05-03. Known ransomware campaign use: Unknown. Forensic triage flag: No.
Apple iOS, iPadOS, and watchOS Mail contains an out-of-bounds write vulnerability which may allow memory modification or application termination when processing a maliciously crafted mail message. (CISA description)
- Vendor / product
- Apple iOS, iPadOS, and watchOS
- CWE
- CWE-787
- CISA required action
- Apply updates per vendor instructions.
- EPSS
- 2.3%, percentile 83 (scored 2026-11-03)
EPSS puts about 2.3 in 100 odds (2.3%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 83% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.
Vendor and reference links (from CISA)
Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.
Frequently asked questions
Is CVE-2020-9818 in the CISA KEV catalogue?
Yes. CISA added CVE-2020-9818 (Apple iOS, iPadOS, and watchOS Out-of-Bounds Write Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2021-11-03. CISA's default due date for it is 2022-05-03.
Is CVE-2020-9818 used in ransomware attacks?
CISA marks known ransomware campaign use as Unknown for CVE-2020-9818. That means CISA lacks confirmation, not that ransomware groups do not use it.
What should I do about CVE-2020-9818?
CISA's required action: Apply updates per vendor instructions.
Sources
- CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
- FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
- NVD record for CVE-2020-9818