CVE-2026-43718: Safari Stack Overflow – Patch, Risk & Detection Guide

Technical summary

CVE-2026-43718 is a stack overflow vulnerability (CWE-121) in Safari's web content processing engine. The vulnerability arises from insufficient input validation when parsing maliciously crafted web content, allowing an attacker to overflow the stack and crash the Safari process. The CVSS 3.1 vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H) reflects network attack capability with low complexity and user interaction requirement, resulting in availability impact only. The fix involves tightened input validation to prevent malformed content from reaching vulnerable stack operations.

Business impact

Safari is a critical user-facing application on Apple devices; unexpected crashes degrade user experience and productivity. For enterprises managing large iOS or macOS fleets, unpatched instances present availability risk during normal browsing. The lack of confidentiality or integrity impact limits direct data-theft risk, but widespread browser crashes can disrupt workflow and support costs. Organizations relying on Safari as their primary browser should prioritize patch deployment to maintain user productivity and system stability.

Affected systems

Vulnerable versions include Safari versions prior to 26.5.2, iOS and iPadOS prior to 26.5.2, macOS Tahoe prior to 26.5.2, tvOS prior to 26.6, visionOS prior to 26.6, and watchOS prior to 26.6. This affects a broad installed base: all iPhone and iPad devices, Mac computers running Tahoe, Apple TV units, Vision Pro, and Apple Watch devices. Organizations with heterogeneous Apple device deployments across all form factors should assume exposure unless updated.

Exploitability

Exploitation requires user interaction—specifically, visiting or interacting with a web page containing maliciously crafted content. There is no indication of pre-authentication bypass or remote code execution. While the attack surface is broad (any webpage can host the payload), the barrier to exploitation is moderate: an attacker must successfully socially engineer or compromise a website to serve the malicious content. The vulnerability is not listed in the CISA KEV catalog, suggesting no evidence of active in-the-wild exploitation at publication date, though this does not guarantee future exploit development.

Remediation

Install Safari 26.5.2 on macOS and compatible systems. For iOS and iPadOS, update to version 26.5.2. For tvOS, visionOS, and watchOS, update to version 26.6. Apple typically bundles these fixes into unified OS updates; administrators should initiate OS updates immediately to close this and concurrent security fixes. Verify patch deployment through device management tools or Software Update settings on user devices.

Patch guidance

Patch availability: Safari 26.5.2, iOS 26.5.2, iPadOS 26.5.2, macOS Tahoe 26.5.2, tvOS 26.6, visionOS 26.6, watchOS 26.6. For macOS, use System Preferences > General > Software Update or Apple's Security Updates page. For iOS and iPadOS, navigate to Settings > General > Software Update. For tvOS, visionOS, and watchOS, check respective system settings. Enterprise administrators should deploy via Mobile Device Management (MDM) solutions to enforce compliance. Prioritize rollout to minimize the window of exposure; stagger deployment if necessary to monitor for conflicts, though stack overflow fixes typically have low regression risk.

Detection guidance

Monitor for unexpected Safari crashes in user logs and crash reports. Endpoint Detection and Response (EDR) solutions may flag unusual process termination patterns if Safari consistently crashes on specific content. Web content filtering can help reduce exposure by blocking known malicious domains, though this does not address zero-day or targeted watering-hole attacks. No specific log signatures distinguish exploitation from other crash causes; detection is primarily reactive (observing crash frequency spikes). Post-patch, sustained crash rates may indicate lingering issues or unpatched systems.

Why prioritize this

This vulnerability merits near-term patching due to (1) wide installed base across consumer and enterprise Apple ecosystems, (2) low attack complexity and user-interaction requirement making exploitation feasible at scale, and (3) high availability impact affecting daily browser operations. Despite a MEDIUM CVSS score, the ubiquity of Safari and the ease of delivering malicious content online justify swift deployment. The absence of KEV listing suggests it is not yet actively exploited, providing a window to patch before threat actors develop reliable exploits.

Risk score, explained

CVSS 3.1 score of 6.5 (MEDIUM) reflects network-exploitable availability impact balanced against user interaction requirement and lack of confidentiality/integrity compromise. The score appropriately captures that a user must visit a malicious page for the crash to occur, limiting automated large-scale attacks. However, the score does not account for Safari's ubiquity; in practical terms, the breadth of potential victim devices elevates organizational risk despite the moderate base score. Security leaders should weight this as a high-priority patch given deployment scale.

Frequently asked questions