Overview
CVE-2025-31266 describes a spoofing vulnerability affecting Apple’s Safari browser (version 18.5) and macOS Sequoia (version 15.5). This flaw could allow a malicious website to potentially spoof the domain name displayed in the title of a pop-up window, potentially misleading users into believing they are interacting with a legitimate site when they are not.
Technical Details
The vulnerability arises from how Safari and macOS handle the truncation of fully qualified domain names (FQDNs) when displaying them in pop-up window titles. The fix implemented in Safari 18.5 and macOS Sequoia 15.5 involves improved truncation logic to prevent malicious websites from crafting FQDNs that, when truncated, display a misleading or entirely different domain.
The specific mechanism by which this spoofing is achieved isn’t publicly documented with extreme detail, likely to avoid providing attackers with further insight. However, it’s assumed that carefully constructed URLs, combined with the browser’s truncation behavior, can lead to the display of an incorrect domain name in the pop-up window title bar.
CVSS Analysis
Currently, the CVE entry lists the severity as N/A and doesn’t provide a CVSS score. This likely indicates that Apple assessed the impact of the vulnerability as relatively low, possibly because it requires user interaction (clicking a link on a malicious website) and the spoofing is limited to the title bar of a pop-up window. However, any spoofing vulnerability presents a risk to users.
Possible Impact
While the severity is marked as N/A, the potential impact of CVE-2025-31266 includes:
- Phishing Attacks: A malicious website could spoof the domain name of a legitimate site in a pop-up window to trick users into entering credentials or sensitive information.
- Reputation Damage: A compromised website could be used to launch spoofing attacks against other legitimate sites, potentially damaging their reputation.
- User Confusion: The misleading domain name could confuse users and lead them to take actions they wouldn’t normally take.
Mitigation or Patch Steps
The primary mitigation for CVE-2025-31266 is to update your Apple devices to the following versions:
- Safari 18.5: Update Safari to version 18.5.
- macOS Sequoia 15.5: Upgrade your macOS to Sequoia 15.5.
Enabling automatic updates is the easiest way to ensure your devices are protected against this and other security vulnerabilities. Exercise caution when clicking links from unknown sources, and always verify the actual URL in the address bar before entering sensitive information.
References
About the security content of Safari 18.5
About the security content of macOS Sequoia 15.5
