CVE-2021-1801
Published: April 11, 2026
Official Description
This issue was addressed with improved iframe sandbox enforcement. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, watchOS 7.3, tvOS 14.4, iOS 14.4 and iPadOS 14.4. Maliciously crafted web content may violate iframe sandboxing policy.
Risk Analysis
This vulnerability in Apple operating systems and watchOS allows maliciously crafted web content to violate iframe sandboxing policy. This could allow an attacker to bypass security restrictions and potentially access sensitive information or execute unauthorized code. The CISA KEV catalog confirms this vulnerability has been actively exploited, highlighting its severity.
This vulnerability has been actively exploited in the wild. The attack vector involves malicious web content, suggesting remote exploitation through web browsing.
Update macOS Big Sur to 11.2, apply Security Update 2021-001 for Catalina and Mojave, update watchOS to 7.3, tvOS to 14.4, and iOS and iPadOS to 14.4. Ensure all Apple devices are kept up-to-date to benefit from improved iframe sandbox enforcement.
Technical Analysis
CVE-2021-1801 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CISA has added CVE-2021-1801 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
Exploit & PoC Resources
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-1801 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1