CVE-2025-54107 Overview
CVE-2025-54107 is a security feature bypass vulnerability in the Windows MapUrlToZone function. The flaw stems from improper resolution of path equivalence [CWE-41], allowing an unauthorized attacker to bypass zone-based security controls over a network. Exploitation requires user interaction, such as convincing a target to open a crafted URL or file. Successful exploitation results in limited confidentiality impact, with no direct effect on integrity or availability. Microsoft has assigned this issue an EPSS score of 0.855% (54.354 percentile), indicating a low observed exploitation likelihood. The vulnerability affects a broad range of supported Windows client and server operating systems.
Critical Impact
An attacker can trick MapUrlToZone into treating untrusted content as belonging to a more trusted security zone, bypassing Windows zone-based protections and exposing limited information.
Affected Products
- Microsoft Windows 10 (versions 1507, 1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (versions 22H2, 23H2, 24H2)
- Microsoft Windows Server 2008, 2012, 2016, 2019, 2022, 2022 23H2, and 2025
Discovery Timeline
- 2025-09-09 - CVE-2025-54107 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-54107
Vulnerability Analysis
The vulnerability resides in MapUrlToZone, a Windows API used by Internet Explorer, Edge legacy components, Office, and other software to determine which security zone a given URL belongs to. Zones such as Internet, Intranet, Trusted, and Restricted drive downstream policy decisions including script execution, file download prompts, and Mark-of-the-Web (MOTW) handling.
Because MapUrlToZone improperly resolves path equivalence, a crafted URL can be canonicalized to a different, more privileged zone than intended. An attacker who lures a user to open a specially crafted link or document can trigger the mismatch and cause Windows to apply weaker restrictions to the content.
The result is a security feature bypass with limited confidentiality impact. While the flaw does not itself grant code execution, it is commonly chained with browser or Office exploits that depend on zone assumptions to complete an attack.
Root Cause
The root cause is improper handling of equivalent path representations [CWE-41]. Multiple string forms, such as UNC variants, alternate slashes, encoded characters, or trailing separators, can refer to the same resource. MapUrlToZone fails to normalize these forms consistently, so different code paths reach different zone conclusions for the same effective target.
Attack Vector
Exploitation requires network delivery and user interaction. An attacker hosts crafted content on a web page, email, or shared file and convinces the victim to open it. When Windows components call MapUrlToZone on the crafted URL, they receive an incorrect, more permissive zone classification and skip security prompts that would normally protect the user.
No authentication is required, and attack complexity is low. However, only content-level information disclosure is achievable directly through this flaw.
Detection Methods for CVE-2025-54107
Indicators of Compromise
- Unusual URLs containing mixed separators, encoded traversal characters, or UNC-style prefixes delivered via email, chat, or web downloads.
- Office or browser processes opening content from remote paths without displaying the expected Protected View or MOTW warning.
- Child processes such as mshta.exe, rundll32.exe, or scripting hosts spawned from Office or browser processes after a user opens a remote link.
Detection Strategies
- Inspect proxy and endpoint logs for URLs with irregular path encodings targeting internal hosts or file shares.
- Correlate user-driven document opens with subsequent network activity to SMB, WebDAV, or HTTP file paths.
- Alert on Windows components loading remote content that bypasses zone-based warning dialogs, based on process command lines and image loads.
Monitoring Recommendations
- Enable auditing of outbound SMB and WebDAV traffic to identify unexpected remote content retrieval.
- Monitor endpoints for missing MOTW attributes on files that originated from external sources.
- Track Microsoft Security Response Center advisories and Windows Update deployment status across the fleet using the Microsoft Security Update guide for CVE-2025-54107.
How to Mitigate CVE-2025-54107
Immediate Actions Required
- Apply the Microsoft security updates referenced in the Microsoft Security Update guide for CVE-2025-54107 to all affected Windows client and server versions.
- Prioritize patching internet-facing systems and user endpoints that regularly process external documents and links.
- Reinforce user awareness training on unsolicited links and documents, since exploitation requires user interaction.
Patch Information
Microsoft has released cumulative updates that address CVE-2025-54107 across all supported Windows versions listed in the advisory. Administrators should validate patch deployment using Windows Update, WSUS, or Microsoft Intune, and confirm applicability for legacy Server 2008, 2012, and 2016 hosts under Extended Security Updates.
Workarounds
- Block outbound SMB (TCP 445) and WebDAV traffic at the perimeter to reduce the ability to fetch attacker-controlled remote paths.
- Enforce Protected View and disable automatic content loading in Microsoft Office to limit user interaction paths.
- Restrict use of the Local Intranet and Trusted Sites zones through Group Policy and remove unnecessary entries.
# Example: disable outbound SMB via Windows Firewall (PowerShell)
New-NetFirewallRule -DisplayName "Block Outbound SMB 445" `
-Direction Outbound `
-Action Block `
-Protocol TCP `
-RemotePort 445 `
-Profile Any
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
