CVE-2026-20644 is a vulnerability in Apple Safari caused by improper memory handling when processing specially crafted web content. The underlying technical issues relate to common memory safety errors such as buffer overflows (CWE-119), use-after-free (CWE-416), and out-of-bounds writes (CWE-787). These memory errors can lead to an unexpected process crash, effectively causing a denial-of-service condition. The vulnerability requires no privileges and can be triggered remotely by enticing a user to visit a maliciously crafted webpage, thus requiring user interaction. Apple fixed the vulnerability by improving memory management in Safari 26.3 and related OS versions, including macOS Tahoe 26.3, iOS 18.7.5, iPadOS 18.7.5, and visionOS 26.3. The CVSS v3.1 base score is 6.5, reflecting medium severity with network attack vector, low attack complexity, no privileges required, user interaction required, and impact limited to availability. No public exploits have been reported, but the vulnerability poses a risk of browser crashes that can disrupt user activities and potentially be used for targeted denial-of-service attacks.

The primary impact of CVE-2026-20644 is on availability, as successful exploitation causes Safari to crash unexpectedly. This can disrupt user productivity and potentially be leveraged in denial-of-service attacks against individuals or organizations relying heavily on Safari for web access. Although confidentiality and integrity are not affected, repeated crashes could degrade user experience and trust in affected Apple platforms. Enterprises with large deployments of Apple devices, especially those using Safari as a primary browser, may face operational interruptions. Additionally, attackers could use this vulnerability as part of multi-stage attacks to distract or disrupt users while attempting other malicious activities. The lack of known exploits reduces immediate risk, but the ease of triggering the crash via crafted web content means the vulnerability should be addressed promptly to avoid exploitation.

Organizations and users should apply the security updates released by Apple immediately, including Safari 26.3 and the corresponding OS updates (macOS Tahoe 26.3, iOS 18.7.5, iPadOS 18.7.5, visionOS 26.3). Beyond patching, network-level protections such as web content filtering and URL reputation services can help block access to potentially malicious sites hosting crafted content. Employing endpoint protection solutions that monitor for abnormal browser crashes or suspicious web activity can provide early detection of exploitation attempts. User education to avoid clicking on untrusted links or visiting suspicious websites reduces the risk of triggering the vulnerability. For organizations, implementing browser isolation or sandboxing technologies can limit the impact of browser crashes on critical systems. Regular vulnerability scanning and asset inventory to identify devices running vulnerable Safari versions will help prioritize remediation efforts.