CVE-2024-23271: Apple Safari XSS Vulnerability

CVE-2024-23271 Overview

CVE-2024-23271 is a logic flaw affecting Apple Safari and multiple Apple operating systems. A malicious website can trigger unexpected cross-origin behavior, undermining the browser's same-origin protections. Apple addressed the issue with improved checks in Safari 17.3, iOS 17.3, iPadOS 17.3, macOS Sonoma 14.3, tvOS 17.3, and watchOS 10.3. The weakness is classified under [CWE-284] Improper Access Control. Exploitation requires user interaction, typically visiting an attacker-controlled page, and can lead to integrity impact on data restricted by the same-origin policy.

Critical Impact
A malicious website may bypass cross-origin restrictions, allowing scripts to interact with resources from unrelated origins and manipulate data outside their trust boundary.

Affected Products

Apple Safari (prior to 17.3)
Apple iOS and iPadOS (prior to 17.3)
Apple macOS Sonoma (prior to 14.3), tvOS (prior to 17.3), and watchOS (prior to 10.3)

Discovery Timeline

2024-04-24 - CVE-2024-23271 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-23271

Vulnerability Analysis

The vulnerability is a logic error in WebKit, the browser engine shared by Safari and Apple's operating systems. Under specific conditions, WebKit failed to enforce cross-origin restrictions correctly. An attacker-controlled page can leverage this weakness to interact with content or state that should be isolated by the same-origin policy. Apple's advisory describes the fix as adding improved checks, indicating the pre-patch code path lacked sufficient validation before permitting cross-origin operations.

Root Cause

The root cause is improper access control [CWE-284] within WebKit's cross-origin enforcement logic. Certain code paths did not validate origin boundaries before granting access to a resource, leaving a gap between the intended security model and its runtime enforcement. Apple's mitigation added explicit checks to close this gap.

Attack Vector

Exploitation is network-based and requires user interaction. The victim must visit a malicious or compromised web page rendered by a vulnerable WebKit build. Once loaded, attacker-controlled JavaScript can trigger the flawed code path to read from, write to, or otherwise influence resources associated with a different origin. No authentication is required. Because the flaw resides in WebKit, any application on iOS, iPadOS, tvOS, watchOS, or macOS that embeds WebKit for rendering may be exposed until patched.

No public proof-of-concept has been released. Refer to the Apple Support Article HT214059 for engine-level context.

Detection Methods for CVE-2024-23271

Indicators of Compromise

Web traffic to unfamiliar domains immediately followed by unexpected authenticated requests to unrelated origins from the same browser session.
Browser telemetry showing cross-origin fetch, XMLHttpRequest, or postMessage activity that violates expected same-origin behavior.
Endpoint records showing Safari or WebKit-based apps running versions earlier than Safari 17.3, iOS/iPadOS 17.3, macOS Sonoma 14.3, tvOS 17.3, or watchOS 10.3.

Detection Strategies

Inventory managed Apple devices and flag any running WebKit builds below the patched versions listed in Apple's advisories.
Monitor web proxy logs for pages that trigger a burst of cross-origin requests to sensitive domains such as identity providers or webmail.
Correlate browser process activity with outbound network requests to identify anomalous origin interactions in enterprise browsers.

Monitoring Recommendations

Ingest endpoint OS and browser version data into a central log store and alert on devices below the patched baseline.
Track user visits to newly registered or low-reputation domains that subsequently attempt cross-origin API calls.
Enable browser security event logging (where available through MDM) to record cross-site script errors and content security policy violations.

How to Mitigate CVE-2024-23271

Immediate Actions Required

Update all Apple devices to Safari 17.3, iOS 17.3, iPadOS 17.3, macOS Sonoma 14.3, tvOS 17.3, or watchOS 10.3 or later.
Push updates through Mobile Device Management (MDM) and enforce compliance for corporate-owned Apple endpoints.
Advise users to avoid untrusted links and unfamiliar websites until patching is complete.

Patch Information

Apple published fixes across its product line. Review the vendor advisories for build-specific details: Apple Support Article HT214055, HT214056, HT214059, HT214060, and HT214061. Consolidated release notes are available at Apple Support Document #120304 and related documents 120306, 120309, 120311, and 120339.

Workarounds

No official workaround exists; patching is the only supported remediation.
Restrict Safari usage on unpatched devices and prefer alternate managed browsers where feasible until updates are deployed.
Enforce strict Content Security Policy (CSP) and CORS headers on sensitive web applications to reduce the impact of cross-origin manipulation.

bash

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

# Query iOS/iPadOS build via MDM (example: Jamf Pro API)
curl -s -u "$JAMF_USER:$JAMF_PASS" \
  "https://your.jamfcloud.com/JSSResource/mobiledevices/id/<device_id>" \
  | xmllint --xpath '//os_version' -