CVE-2024-44155 Overview
CVE-2024-44155 is an input validation flaw in Apple's custom URL scheme handling across Safari and multiple operating systems. Maliciously crafted web content can violate the iframe sandboxing policy, undermining a core browser isolation boundary. Apple addressed the issue with improved input validation in Safari 18, iOS 17.7.1 and iPadOS 17.7.1, iOS 18 and iPadOS 18, macOS Sequoia 15, and watchOS 11. Exploitation requires user interaction such as visiting an attacker-controlled page, and the primary impact is to integrity rather than confidentiality or availability.
Critical Impact
Attackers can bypass iframe sandbox restrictions to launch or interact with applications through custom URL schemes, enabling cross-context integrity attacks against users who visit malicious web content.
Affected Products
- Apple Safari (prior to Safari 18)
- Apple iOS and iPadOS (prior to 17.7.1 and 18)
- Apple macOS Sequoia (prior to 15) and Apple watchOS (prior to 11)
Discovery Timeline
- 2024-10-28 - CVE-2024-44155 published to the National Vulnerability Database (NVD)
- 2026-06-17 - Last updated in the NVD database
Technical Details for CVE-2024-44155
Vulnerability Analysis
The vulnerability resides in how WebKit-based components parse and dispatch custom URL schemes referenced from within sandboxed iframes. The HTML iframesandbox attribute is designed to restrict framed content from executing scripts, submitting forms, or triggering top-level navigation without explicit opt-in tokens such as allow-top-navigation or allow-popups. Because of insufficient input validation on custom scheme URLs, framed content can escape those restrictions and cause navigation or handler invocation outside the sandbox context.
The result is a policy violation that lets malicious pages influence host application behavior through registered URL handlers. Since custom schemes frequently launch native applications with attacker-supplied parameters, the integrity impact extends beyond the browser and into the operating system.
Root Cause
Apple's advisories attribute the issue to insufficient validation of custom URL scheme inputs. The NVD entry lists the weakness as [NVD-CWE-noinfo], with the underlying defect being an improper input validation issue in URL dispatch logic that failed to reconcile scheme handling with iframe sandbox tokens.
Attack Vector
Exploitation is network-based and requires user interaction. An attacker hosts crafted web content, typically containing a sandboxed iframe that references a custom URL scheme. When the victim loads the page, the browser processes the URL in a way that bypasses sandbox restrictions, invoking a registered protocol handler or navigating the top-level frame. No authentication is required, and the technique can be delivered through phishing links, malicious ads, or compromised sites.
No public proof-of-concept exploit is listed in the enriched data, and the vulnerability is not tracked on the CISA Known Exploited Vulnerabilities catalog. Refer to the Full Disclosure Mailing List Post for community discussion of related Apple October 2024 issues.
Detection Methods for CVE-2024-44155
Indicators of Compromise
- Unexpected launches of applications registered as custom URL scheme handlers immediately after browser sessions on unpatched Apple devices.
- Web server or proxy logs showing HTML responses containing sandboxed iframe elements that reference non-standard URI schemes.
- Endpoint telemetry showing Safari or WebKit spawning URL handler processes with parameters sourced from third-party origins.
Detection Strategies
- Inventory Apple endpoints and correlate installed Safari, iOS, iPadOS, macOS, and watchOS versions against the fixed builds in Apple's advisories.
- Inspect HTTP responses at the proxy layer for iframe elements combining the sandbox attribute with attacker-controlled src values pointing to custom schemes.
- Hunt for anomalous parent-child process relationships where a browser process invokes a URL-scheme handler outside expected user workflows.
Monitoring Recommendations
- Forward browser and OS process telemetry from macOS endpoints to a centralized analytics platform and alert on URL handler executions initiated by web content.
- Track mobile device management (MDM) compliance for iOS 17.7.1, iOS 18, iPadOS, macOS Sequoia 15, and watchOS 11 updates.
- Monitor threat intelligence feeds for updates to the Apple advisories referenced in NVD, including Apple Security Advisory 121238 and Apple Security Advisory 121240.
How to Mitigate CVE-2024-44155
Immediate Actions Required
- Update all Apple devices to Safari 18, iOS 17.7.1 or 18, iPadOS 17.7.1 or 18, macOS Sequoia 15, and watchOS 11 or later.
- Prioritize patching for users who browse untrusted content or handle sensitive data on Apple endpoints.
- Communicate phishing awareness guidance emphasizing risk from unsolicited links that render iframes or trigger app launches.
Patch Information
Apple released fixes across multiple platforms. Consult the vendor advisories for exact build numbers and installation instructions: Apple Security Advisory 121238, Apple Security Advisory 121240, Apple Security Advisory 121241, Apple Security Advisory 121250, and Apple Security Advisory 121567.
Workarounds
- Restrict browsing to trusted domains through corporate web filtering until patches are deployed.
- Disable or remove unnecessary custom URL scheme handlers on managed macOS and iOS devices via MDM configuration profiles.
- Enforce MDM policies that mandate automatic OS updates and block installation of applications that register broad custom URL schemes.
# Verify Safari and macOS versions on managed endpoints
sw_vers
defaults read /Applications/Safari.app/Contents/Info.plist CFBundleShortVersionString
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
