CVE-2026-43721: Apple Safari Information Disclosure Flaw

CVE-2026-43721 Overview

CVE-2026-43721 is a clipboard hijacking vulnerability affecting Apple Safari, iOS, iPadOS, and macOS. A malicious website can silently read or overwrite clipboard data without proper user authorization. The flaw is categorized under [CWE-732] (Incorrect Permission Assignment for Critical Resource) and stems from insufficient state management around clipboard access controls. Apple addressed the issue through improved state management in Safari 26.5.2, iOS 26.5.2, iPadOS 26.5.2, and macOS Tahoe 26.5.2. Exploitation requires user interaction with the attacker-controlled site but does not require authentication or elevated privileges.

Critical Impact
A malicious website can silently hijack clipboard contents, exposing sensitive data such as passwords, cryptocurrency wallet addresses, one-time codes, and copied session tokens.

Affected Products

Apple Safari (prior to 26.5.2)
Apple iOS and iPadOS (prior to 26.5.2)
Apple macOS Tahoe (prior to 26.5.2)

Discovery Timeline

2026-06-29 - CVE-2026-43721 published to NVD
2026-06-30 - Last updated in NVD database

Technical Details for CVE-2026-43721

Vulnerability Analysis

The vulnerability resides in how Safari's WebKit engine manages state around clipboard read and write operations. Browsers typically require an explicit user gesture, such as a paste command or a permission prompt, before a page can access clipboard contents. In this case, a state management flaw allows a crafted page to bypass those gating controls and interact with the clipboard silently.

Because the clipboard often holds transient but sensitive data, silent read access enables direct exfiltration of secrets that never touch the page's DOM. Silent write access enables clipboard poisoning attacks, in which an adversary replaces a copied cryptocurrency address or shell command with attacker-controlled content that the victim later pastes into a wallet or terminal.

Root Cause

Apple's advisory describes the root cause as improper state management in the clipboard permission model. The engine fails to correctly track whether a valid user gesture authorizes the current clipboard operation. This is consistent with [CWE-732], where a critical resource is exposed with weaker permission checks than intended.

Attack Vector

Exploitation occurs over the network. A victim must visit or interact with a malicious website using a vulnerable Safari or WebKit-based browser. Once loaded, the page invokes clipboard APIs while the engine's state check incorrectly treats the operation as authorized. No credentials, prompts, or additional privileges are required.

See the Apple Support Article #127594, Apple Support Article #127595, and Apple Support Article #127685 for vendor technical details.

Detection Methods for CVE-2026-43721

Indicators of Compromise

Web traffic to untrusted domains immediately followed by user reports of altered clipboard content, such as swapped cryptocurrency addresses or unexpected command strings.
Browser telemetry showing Safari or WebKit versions below 26.5.2 on macOS, iOS, or iPadOS endpoints.
User-agent strings from vulnerable Safari builds accessing high-risk sites flagged by threat intelligence.

Detection Strategies

Inventory managed Apple endpoints and identify devices running Safari, iOS, iPadOS, or macOS Tahoe versions older than 26.5.2.
Monitor DNS and proxy logs for connections to newly registered or low-reputation domains from Safari user agents.
Correlate helpdesk tickets referencing clipboard corruption, mistyped wallet transfers, or unexpected paste content with recent browsing activity.

Monitoring Recommendations

Enable browser version reporting through mobile device management (MDM) to track patch compliance across the Apple fleet.
Alert on execution of unusual commands pasted into terminals or wallet applications shortly after Safari sessions.
Ingest web proxy logs into a centralized analytics platform to hunt for repeated clipboard-abusing script patterns.

How to Mitigate CVE-2026-43721

Immediate Actions Required

Update Safari to version 26.5.2 on macOS immediately.
Update iOS and iPadOS devices to 26.5.2 through MDM policy or user prompts.
Update macOS Tahoe to 26.5.2 to receive the WebKit fix that also protects other WebKit-based apps.
Advise users to avoid copying high-value secrets, such as wallet addresses or passwords, while browsing untrusted sites on unpatched devices.

Patch Information

Apple fixed the vulnerability through improved state management in Safari 26.5.2, iOS 26.5.2, iPadOS 26.5.2, and macOS Tahoe 26.5.2. Refer to Apple Support Article #127594, Apple Support Article #127595, and Apple Support Article #127685 for the official release notes and installation instructions.

Workarounds

Restrict use of Safari on unpatched devices for sensitive workflows involving copy-paste of credentials or cryptocurrency addresses.
Configure MDM to enforce minimum OS and Safari versions, blocking access to corporate resources from noncompliant devices.
Use password managers that inject credentials directly into fields rather than relying on clipboard copy-paste.

bash

# Verify installed Safari version on macOS
mdls -name kMDItemVersion /Applications/Safari.app

# Verify macOS build to confirm 26.5.2 (Tahoe) or later
sw_vers

# Enforce minimum OS version via MDM (example configuration profile key)
# PayloadType: com.apple.softwareupdate
# Key: MinimumOSVersion  Value: 26.5.2