CVE-2026-43718 Overview
CVE-2026-43718 is a stack overflow vulnerability [CWE-121] affecting Apple Safari and multiple Apple operating systems. Processing maliciously crafted web content can cause an unexpected Safari crash. Apple addressed the flaw with improved input validation in Safari 26.5.2, iOS 26.5.2, iPadOS 26.5.2, and macOS Tahoe 26.5.2.
The vulnerability requires user interaction, such as visiting a malicious website. An attacker cannot read or modify data through this bug, but they can reliably terminate the browser process. The issue impacts the availability of the Safari browser across Apple's desktop and mobile platforms.
Critical Impact
Attackers hosting crafted web content can trigger a stack overflow in Safari, causing the browser to crash on visit and disrupting user sessions across iOS, iPadOS, and macOS.
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-2026-43718 published to NVD
- 2026-06-30 - Last updated in NVD database
Technical Details for CVE-2026-43718
Vulnerability Analysis
CVE-2026-43718 is classified as a stack-based buffer overflow [CWE-121] in Safari's web content processing path. When Safari parses specific malformed structures in attacker-controlled web content, a routine writes beyond the bounds of a stack-allocated buffer. The result is corruption of adjacent stack memory and an unexpected process termination.
Apple's advisory states the fix consisted of improved input validation, indicating that the vulnerable code path failed to correctly validate the size or shape of input before copying data onto the stack. The disclosed impact is limited to a crash, meaning availability is affected but confidentiality and integrity are not.
Root Cause
The root cause is missing or insufficient bounds checking on web content data processed by Safari's rendering engine. Untrusted input reaches a fixed-size stack buffer without validation, allowing a length or field value under attacker control to exceed the buffer size. Apple's remediation adds input validation to reject or truncate malformed content before it corrupts the stack frame.
Attack Vector
Exploitation requires a victim to load attacker-controlled web content in Safari or a WebKit-based view. The attacker hosts the crafted page on a website, delivers it through a link in email or messaging, or embeds it in an in-app browser view. When Safari parses the content, the stack overflow triggers and the browser crashes. No authentication is required, but user interaction is necessary to visit the page.
The vulnerability manifests during content parsing. Refer to the Apple Support Document #127594, Apple Support Document #127595, and Apple Support Document #127685 for vendor technical details.
Detection Methods for CVE-2026-43718
Indicators of Compromise
- Repeated unexpected Safari process crashes correlated with visits to specific URLs or domains.
- Crash reports on macOS in ~/Library/Logs/DiagnosticReports/ referencing Safari or WebKit with stack corruption signatures.
- iOS and iPadOS crash logs (available via Settings > Privacy & Security > Analytics & Improvements > Analytics Data) naming Safari or WebKit.
- Outbound web traffic to newly registered or low-reputation domains immediately preceding browser termination.
Detection Strategies
- Monitor endpoint telemetry for abnormal Safari and com.apple.WebKit.WebContent process exits, especially clustered across multiple users.
- Correlate browser crash events with proxy or DNS logs to identify URLs that consistently precede termination.
- Track Safari and WebKit version strings across the fleet to identify unpatched endpoints running builds prior to 26.5.2.
Monitoring Recommendations
- Ingest macOS unified logs and iOS device analytics into a centralized logging platform for correlation.
- Alert on any endpoint still reporting a Safari, iOS, iPadOS, or macOS Tahoe version below 26.5.2.
- Baseline normal Safari crash rates per user and flag statistically significant deviations for investigation.
How to Mitigate CVE-2026-43718
Immediate Actions Required
- Update Safari to version 26.5.2 on all managed macOS endpoints.
- Update iOS and iPadOS devices to 26.5.2 through MDM policy or user prompt.
- Update macOS Tahoe systems to 26.5.2 to receive the patched WebKit components.
- Advise users to avoid untrusted links until the update is applied.
Patch Information
Apple released fixes in Safari 26.5.2, iOS 26.5.2, iPadOS 26.5.2, and macOS Tahoe 26.5.2. The vendor states the issue was addressed with improved input validation. Consult the Apple Support Document #127594, Apple Support Document #127595, and Apple Support Document #127685 for release details and download instructions.
Workarounds
- Use an alternate, patched browser on macOS until Safari can be updated.
- Restrict browsing to trusted sites and block known malicious domains at the network egress or DNS layer.
- Enforce MDM configuration profiles that require the minimum patched OS version before granting access to corporate resources.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
