CVE-2021-1879

What is this vulnerability?

CVE-2021-1879 is categorized as a medium Cross-Site Scripting (XSS) flaw with a CVSS base score of 6.1. Based on our vulnerability intelligence, this issue occurs when the application fails to securely handle untrusted data boundaries.

This issue was addressed by improved management of object lifetimes. This issue is fixed in iOS 12.5.2, iOS 14.4.2 and iPadOS 14.4.2, watchOS 7.3.3. Processing maliciously crafted web content may lead to universal cross site scripting. Apple is aware of a report that this issue may have been actively exploited..

This architectural defect enables adversaries to bypass intended security controls, directly manipulating the application's execution state or data layer. Immediate strategic intervention is required.

Risk Assessment

Impact on Systems

✅ Data Exfiltration: Attackers can extract sensitive data from backend databases, configuration files, or internal services.

✅ Authentication Bypass: Exploiting this flaw may allow unauthorized access to protected resources and administrative interfaces.

✅ Lateral Movement: Once initial access is gained, attackers can pivot to internal systems and escalate privileges.

How to Fix and Mitigate CVE-2021-1879

1. Apply Vendor Patches Immediately: This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog. Apply updates per vendor instructions.
2. Verify Patch Deployment: Confirm all instances are updated using Precogs continuous monitoring.
3. Review Audit Logs: Investigate historical access logs for indicators of compromise related to this attack surface.
4. Implement Defense-in-Depth: Deploy WAF rules, network segmentation, and endpoint detection to limit blast radius.

Defending with Precogs AI

WebKit improperly manages object lifetimes, allowing maliciously crafted web content to trigger universal cross-site scripting (UXSS). Attackers exploit this to steal sensitive cross-origin data. Precogs Application Security Module maps untrusted object lifecycles to security boundary violations.

Use Precogs to continuously scan your codebase, binaries, APIs, and infrastructure for this vulnerability class and related attack patterns. Our AI-powered detection engine combines static analysis with threat intelligence to identify exploitable weaknesses before attackers do.

Start scanning with Precogs →

Vulnerability Code Signature

Attack Data Flow

Vulnerable Code Pattern

// ❌ VULNERABLE: Direct DOM injection
const userComment = urlParams.get('comment');
// Taint sink: innerHTML executes injected scripts
document.getElementById('comments').innerHTML = userComment;

Secure Code Pattern

// ✅ SECURE: Safe DOM manipulation
const userComment = urlParams.get('comment');
// Sanitized binding: textContent escapes HTML entities
document.getElementById('comments').textContent = userComment;

How Precogs Detects This

Precogs AI Analysis Engine maps untrusted input sources directly to sensitive DOM manipulation functions, detecting Cross-Site Scripting (XSS) paths before deployment.\n