CVE-2026-39872: Safari Memory Handling Vulnerability – CVSS 6.5

Technical summary

The vulnerability stems from improper memory handling in Safari's web content processing engine, classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-416 (Use After Free). The flaw allows specially crafted web content to trigger an out-of-bounds access or use-after-free condition, causing an unexpected process termination. The attack vector is network-based with low complexity; it requires user interaction (clicking a link or viewing embedded content) but no prior authentication or elevated privileges. The impact is limited to availability—the affected process crashes, but the system remains otherwise functional and no sensitive data is exposed.

Business impact

Frequent crashes of Safari or system processes degrade user experience and productivity, particularly for organizations relying on Safari for development, testing, or daily browsing. In enterprise environments, if users are directed to malicious content via phishing or compromised advertising networks, the disruption can affect staff availability. The vulnerability does not enable data theft, lateral movement, or privilege escalation, so business continuity and confidentiality are not directly threatened. However, the ease of triggering a crash (malicious webpage visits) makes it a potential vector for denial-of-service campaigns targeting specific user populations.

Affected systems

Apple Safari, iOS, iPadOS, macOS, tvOS, visionOS, and watchOS are vulnerable. Specific fixed versions include Safari 26.5.2, iOS 26.5.2, iPadOS 26.5.2, macOS Tahoe 26.5.2, tvOS 26.6, visionOS 26.6, and watchOS 26.6. All users running versions prior to these fixed releases on any of these platforms are at risk. The threat is particularly relevant to organizations with large macOS or iOS populations, or those managing corporate Apple device fleets.

Exploitability

Exploitation requires user interaction—the victim must visit or be directed to a webpage containing the malicious content. There is no known exploit in the CISA KEV catalog, and public exploit code has not been disclosed. However, the low complexity of the attack (a simple webpage) and the ubiquity of web browsing make this a feasible attack vector. An attacker could distribute the malicious webpage via email phishing, compromised advertising networks, or drive-by downloads. The barrier to weaponization is low, and the attack can be launched remotely without authentication.

Remediation

Immediate action: update all affected Apple devices to the patched versions—Safari 26.5.2 or later, iOS/iPadOS 26.5.2 or later, macOS Tahoe 26.5.2 or later, or tvOS/visionOS/watchOS 26.6 or later depending on the platform. Enable automatic updates where possible to prevent similar flaws in future releases. Administratively, consider restricting access to untrusted websites via web filters and educating users to avoid clicking suspicious links. For development environments, use sandboxed browsers or isolated VMs when testing web content from untrusted sources.

Patch guidance

Apple has released patches across all affected platforms. iOS, iPadOS, and Safari users should prioritize updating to 26.5.2; macOS users should update to Tahoe 26.5.2; and tvOS, visionOS, and watchOS users should update to 26.6. Enterprise administrators should use Mobile Device Management (MDM) solutions to enforce automatic updates across iOS and iPadOS devices. For macOS, configuration management tools can push the latest OS version or Safari update. Verify compatibility with your organization's critical applications before deploying updates, though the severity and nature of this fix suggest low risk of regression. Test the update in a small user group first if your environment is sensitive.

Detection guidance

Monitor system logs for unexpected Safari process crashes or watchdog resets on macOS and iOS devices. Look for patterns of crashes correlated with specific websites or web content—repeated crashes from similar sources may indicate an active attack. Network detection is limited since the attack occurs within legitimate HTTPS traffic; however, monitoring for spikes in web traffic to suspicious domains combined with crash logs can help identify compromised or malicious websites. On managed devices, use MDM to collect crash reports and correlate them with browser behavior. Review web proxy logs for attempts to access known malicious content distribution sites.

Why prioritize this

This vulnerability merits prompt but not emergency attention. The CVSS score of 6.5 (Medium) reflects high availability impact but zero confidentiality or integrity risk. Prioritize patching for users who frequently browse untrusted content (developers, security researchers, customer-facing staff) and publicly accessible systems. Organizations with strict change control windows should plan patching within the next 4–6 weeks. The absence of known active exploitation and KEV status reduces urgency compared to critical flaws, but the ease of triggering a crash means delaying patches beyond 8 weeks is imprudent.

Risk score, explained

The CVSS 3.1 score of 6.5 reflects a Medium severity: the attack vector is Network (AV:N) and requires low complexity (AC:L) with user interaction (UI:R), but no special privileges (PR:N). The impact scope is Unchanged (S:U). Critically, there is no impact on Confidentiality (C:N) or Integrity (I:N)—the flaw only affects Availability (A:H), causing a process crash. This bounds the overall severity; the risk is operational disruption rather than data compromise. The score accurately reflects a real but contained threat that demands attention but does not justify emergency response protocols.

Frequently asked questions