CVE-2025-30466: Apple Safari Auth Bypass Vulnerability

CVE-2025-30466 Overview

CVE-2025-30466 is a Same Origin Policy bypass vulnerability affecting Apple Safari and multiple Apple operating systems. The vulnerability stems from improper state management in the WebKit browser engine, allowing malicious websites to bypass the Same Origin Policy—a critical browser security mechanism that prevents scripts from one origin from accessing data from another origin.

Critical Impact

This vulnerability enables websites to bypass the Same Origin Policy, potentially allowing attackers to steal sensitive data, session tokens, and credentials from other websites the user has open or has authenticated to.

Affected Products

• Apple Safari versions prior to 18.4
• Apple iOS and iPadOS versions prior to 18.4
• Apple macOS Sequoia versions prior to 15.4
• Apple visionOS versions prior to 2.4

Discovery Timeline

• 2025-05-29 - CVE-2025-30466 published to NVD
• 2025-06-02 - Last updated in NVD database

Technical Details for CVE-2025-30466

Vulnerability Analysis

This vulnerability is classified under CWE-346 (Origin Validation Error), which describes flaws where a system fails to properly verify that the source of data or communication is valid. In the context of web browsers, the Same Origin Policy (SOP) is the fundamental security boundary that isolates web content from different origins, preventing malicious scripts on one page from obtaining access to sensitive data on another page.

The vulnerability allows an attacker-controlled website to circumvent these protections, effectively breaking the security isolation between web applications. This can lead to unauthorized access to sensitive information including authentication cookies, session identifiers, personal data, and other confidential content from cross-origin resources.

Root Cause

The root cause of CVE-2025-30466 lies in improper state management within WebKit, the browser engine powering Safari and embedded browsers across Apple platforms. State management flaws can occur when the browser incorrectly tracks or validates the origin context during cross-origin operations, creating windows where the SOP enforcement fails.

Apple addressed this issue through improved state management mechanisms that properly validate and maintain origin context throughout browser operations, ensuring the Same Origin Policy is consistently enforced.

Attack Vector

The attack vector for this vulnerability is network-based and requires no authentication or user interaction beyond visiting a malicious website. An attacker would need to:

1. Host a malicious website containing exploit code
2. Lure a victim to visit the malicious site (via phishing, malvertising, or compromised legitimate sites)
3. The malicious script executes in the victim's browser and bypasses SOP restrictions
4. Sensitive data from other origins the victim has access to can be exfiltrated

Since the vulnerability requires no privileges and no user interaction beyond navigation, it presents a significant threat to users browsing untrusted content. The attack can be delivered through malicious advertisements, compromised websites, or targeted phishing campaigns.

Detection Methods for CVE-2025-30466

Indicators of Compromise

• Unusual cross-origin network requests originating from browser processes
• JavaScript execution patterns attempting to access resources from foreign origins
• Unexpected data exfiltration to unknown external domains following web browsing sessions
• Browser console errors or warnings related to cross-origin resource access attempts

Detection Strategies

• Monitor browser network traffic for anomalous cross-origin requests that bypass expected CORS restrictions
• Implement network monitoring to detect data exfiltration patterns following visits to untrusted websites
• Review browser logs for unusual WebKit process behavior or unexpected cross-origin data access
• Deploy endpoint detection solutions capable of monitoring browser process memory and network behavior

Monitoring Recommendations

• Enable comprehensive logging on network security devices to capture browser traffic patterns
• Implement Content Security Policy (CSP) headers on critical web applications to provide defense-in-depth
• Monitor for unusual authentication token usage or session anomalies across web applications
• Configure SentinelOne agents to monitor for suspicious browser process behavior and network communications

How to Mitigate CVE-2025-30466

Immediate Actions Required

• Update Safari to version 18.4 or later immediately
• Update iOS and iPadOS devices to version 18.4 or later
• Update macOS Sequoia to version 15.4 or later
• Update visionOS devices to version 2.4 or later
• Avoid visiting untrusted websites until patches are applied

Patch Information

Apple has released security updates addressing this vulnerability across all affected platforms. Detailed patch information is available through the following Apple Security Advisories:

• Apple Support Advisory #122371 - Safari 18.4
• Apple Support Advisory #122373 - iOS 18.4 and iPadOS 18.4
• Apple Support Advisory #122378 - macOS Sequoia 15.4
• Apple Support Advisory #122379 - visionOS 2.4

Organizations should prioritize deployment of these updates given the critical severity and the potential for sensitive data exposure.

Workarounds

• Use alternative browsers (non-WebKit based) on macOS until Safari can be updated
• Implement strict network segmentation to limit exposure of sensitive web applications
• Enable enhanced browser security settings and disable JavaScript on untrusted sites where feasible
• Deploy web filtering solutions to block access to known malicious domains

# Check Safari version on macOS
/Applications/Safari.app/Contents/MacOS/Safari --version

# Verify macOS version
sw_vers -productVersion

# Force software update check on macOS
softwareupdate --list