---
id: "CVE-2020-9818"
kind: "vulnerability"
aliases: ["CVE-2020-9818"]
title: "Apple iOS, iPadOS, and watchOS: Apple iOS, iPadOS, and watchOS Out-of-Bounds Write Vulnerability"
severity: "high"
cvss: 8.8
epss: 0.02286
exploited: true
status: "open"
category: "vendor"
products: [{"name": "Apple iOS, iPadOS, and watchOS", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["apple-mail", "exploited", "ios", "ipados", "vendor", "watchos"]
not_affected_if: ["fully-patched-devices"]
published_at: "2020-06-09T17:15:13+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-9818", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2020-9818", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-9818", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Apple iOS, iPadOS, and watchOS: Apple iOS, iPadOS, and watchOS Out-of-Bounds Write Vulnerability

Apple's iOS, iPadOS and watchOS Mail app has an out-of-bounds write flaw triggered when it processes a specially crafted email. An attacker can corrupt memory, which can crash the app or be used to modify memory during an attack.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Apple iOS, iPadOS, and watchOS affected ? fixed ?

## Fix

Update iOS, iPadOS and watchOS to a release that includes Apple's fix; CISA says to apply updates per vendor instructions.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-9818
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2020-9818
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2020-9818

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_