CVE-2025-26663: Windows 10 1507 Use-After-Free Flaw

CVE-2025-26663 Overview

CVE-2025-26663 is a critical use-after-free vulnerability in the Windows Lightweight Directory Access Protocol (LDAP) implementation. This memory corruption flaw allows an unauthorized attacker to execute arbitrary code over a network without requiring authentication or user interaction. The vulnerability affects the LDAP client component across a wide range of Microsoft Windows operating systems, including both desktop and server editions.

Use-after-free vulnerabilities occur when a program continues to use a pointer after the memory it references has been freed, potentially allowing attackers to manipulate the freed memory region to achieve code execution. In this case, the LDAP service improperly handles memory during protocol operations, creating an exploitable condition for remote attackers.

Critical Impact

Remote unauthenticated attackers can achieve arbitrary code execution on vulnerable Windows systems by exploiting the LDAP service, potentially leading to complete system compromise across enterprise environments.

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, 2025

Discovery Timeline

• 2025-04-08 - CVE-2025-26663 published to NVD
• 2025-07-10 - Last updated in NVD database

Technical Details for CVE-2025-26663

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption vulnerability class that occurs when a program continues to reference memory after it has been deallocated. In the context of Windows LDAP, the vulnerability exists in how the LDAP client handles certain protocol operations, leading to a dangling pointer condition.

The attack can be executed over a network without requiring any privileges or user interaction, making it particularly dangerous for internet-facing systems and internal networks where LDAP traffic is common. Successful exploitation could result in complete system compromise, including unauthorized access to sensitive directory information, lateral movement capabilities, and persistent access to domain infrastructure.

Windows LDAP is a critical component used extensively in Active Directory environments for authentication, authorization, and directory queries. This makes the vulnerability particularly impactful in enterprise environments where LDAP is heavily utilized for identity management and authentication services.

Root Cause

The root cause is improper memory management in the Windows LDAP client implementation. When processing certain LDAP operations, the code fails to properly track memory allocations and deallocations, resulting in a use-after-free condition. The freed memory can be reallocated and controlled by an attacker, who can then manipulate the contents to hijack program execution flow when the dangling pointer is dereferenced.

Attack Vector

The attack vector is network-based, requiring the attacker to send specially crafted LDAP requests to a vulnerable Windows system. The exploitation does not require authentication, user interaction, or elevated privileges, significantly lowering the barrier for successful attacks.

An attacker could exploit this vulnerability by:

1. Sending malicious LDAP packets to a target Windows system
2. Triggering the memory deallocation while maintaining a reference to the freed memory
3. Controlling the contents of the reallocated memory region
4. Causing the LDAP service to dereference the stale pointer, executing attacker-controlled code

The vulnerability can be exploited through standard LDAP ports (TCP 389 for LDAP, TCP 636 for LDAPS), making network-level detection and blocking potentially challenging in environments that rely on LDAP services.

Detection Methods for CVE-2025-26663

Indicators of Compromise

• Unusual LDAP traffic patterns or malformed LDAP requests targeting Windows systems
• Unexpected crashes or restarts of LDAP-related services (lsass.exe, dsamain.exe)
• Memory corruption indicators in Windows Event logs related to LDAP operations
• Suspicious network connections to LDAP ports (389/636) from unauthorized sources

Detection Strategies

• Deploy network intrusion detection systems (IDS) rules to identify anomalous LDAP traffic patterns
• Monitor Windows Event logs for Application crashes involving lsass.exe or LDAP-related components
• Implement behavioral analysis to detect unusual LDAP query patterns or responses
• Use SentinelOne's behavioral AI to detect exploitation attempts and memory corruption techniques

Monitoring Recommendations

• Enable detailed logging for LDAP operations on Windows systems, particularly on Domain Controllers
• Configure network monitoring to alert on LDAP traffic from unexpected sources or to unusual destinations
• Implement SentinelOne Singularity platform for real-time endpoint detection and response capabilities targeting memory exploitation techniques

How to Mitigate CVE-2025-26663

Immediate Actions Required

• Apply the Microsoft security update immediately on all affected Windows systems, prioritizing Domain Controllers and systems with exposed LDAP services
• Restrict LDAP access to trusted network segments using firewall rules and network segmentation
• Audit systems for signs of compromise before and after patching
• Consider temporarily disabling external LDAP access if patching cannot be performed immediately

Patch Information

Microsoft has released security updates to address this vulnerability as part of their security update cycle. Administrators should obtain and apply the appropriate patches from the Microsoft Security Update Guide for CVE-2025-26663.

The security update addresses the use-after-free vulnerability by correcting how the Windows LDAP implementation manages memory during protocol operations. All affected Windows versions have corresponding patches available through Windows Update, WSUS, and the Microsoft Update Catalog.

Workarounds

• Implement network segmentation to limit LDAP service exposure to only necessary clients and networks
• Use firewall rules to restrict inbound connections to LDAP ports (389, 636) from untrusted networks
• Deploy LDAP channel binding and LDAP signing to add additional protocol-level protections
• Consider using VPN or other secure tunneling for remote LDAP access requirements

# Windows Firewall rule to restrict LDAP access (PowerShell)
New-NetFirewallRule -DisplayName "Restrict LDAP Access" `
    -Direction Inbound `
    -Protocol TCP `
    -LocalPort 389,636 `
    -Action Block `
    -RemoteAddress "0.0.0.0/0" `
    -Enabled True

# Allow LDAP only from trusted subnet
New-NetFirewallRule -DisplayName "Allow LDAP from Trusted Network" `
    -Direction Inbound `
    -Protocol TCP `
    -LocalPort 389,636 `
    -Action Allow `
    -RemoteAddress "10.0.0.0/8" `
    -Enabled True