CVE-2025-58107: Exchange ActiveSync Info Disclosure Flaw

CVE-2025-58107 Overview

CVE-2025-58107 is a sensitive data exposure vulnerability affecting Microsoft Exchange Server through version 2019. The flaw exists in Exchange ActiveSync (EAS) configurations on on-premises servers, where sensitive data from Samsung mobile devices may be transmitted in cleartext. This exposed data includes the user's name, email address, device ID, bearer token, and base64-encoded password.

Critical Impact

Attackers capable of intercepting network traffic can capture user credentials and authentication tokens, potentially leading to unauthorized access to corporate email accounts and impersonation attacks.

Affected Products

• Microsoft Exchange Server 2019 and earlier versions
• Microsoft Exchange ActiveSync (EAS) protocol implementations
• Samsung mobile devices configured with Exchange ActiveSync

Discovery Timeline

• 2026-03-02 - CVE CVE-2025-58107 published to NVD
• 2026-03-02 - Last updated in NVD database

Technical Details for CVE-2025-58107

Vulnerability Analysis

This vulnerability is classified under CWE-319 (Cleartext Transmission of Sensitive Information). The core issue stems from the Exchange ActiveSync protocol's handling of authentication data when Samsung mobile devices synchronize with on-premises Exchange servers. Rather than enforcing encrypted transmission of credentials, the EAS configuration allows sensitive authentication elements to be sent in cleartext across the network.

The vulnerability is particularly concerning because the transmitted data includes not only user identifiers like name and email address, but also authentication credentials including bearer tokens and passwords encoded in base64. Base64 encoding provides no cryptographic protection and can be trivially decoded by any attacker who intercepts the traffic.

Root Cause

The root cause lies in the legacy ActiveSync protocol's configuration behavior with Samsung mobile devices. The protocol implementation fails to enforce TLS encryption for all authentication data exchanges, or may downgrade to unencrypted communication under certain conditions. This creates an opportunity for network-based attackers to capture sensitive credentials during the device synchronization process.

Attack Vector

The attack vector is network-based, requiring the attacker to be positioned to intercept traffic between the Samsung mobile device and the Exchange server. This could be achieved through:

• Man-in-the-middle attacks on corporate or public wireless networks
• Compromised network infrastructure between the mobile device and Exchange server
• ARP spoofing or DNS hijacking on local network segments

An attacker intercepting the cleartext traffic can extract the base64-encoded password and decode it to obtain the user's actual credentials. The bearer token can also be captured and potentially replayed for unauthorized access to the victim's email account.

The vulnerability requires no authentication or user interaction to exploit, making it particularly dangerous in environments where network security controls are weak or where users connect through untrusted networks.

Detection Methods for CVE-2025-58107

Indicators of Compromise

• Unencrypted HTTP traffic on port 80 containing ActiveSync protocol headers (MS-ASProtocolVersion, MS-ASProtocolCommand)
• Network captures showing base64-encoded credential strings in cleartext HTTP payloads
• Authentication anomalies where user sessions originate from unexpected IP addresses following mobile device sync operations
• Unusual ActiveSync connection patterns from Samsung device identifiers

Detection Strategies

• Deploy network intrusion detection systems (NIDS) configured to alert on unencrypted ActiveSync protocol traffic
• Monitor for HTTP traffic to Exchange servers that should be enforcing HTTPS-only connections
• Implement SSL/TLS inspection to verify all ActiveSync communications are properly encrypted
• Review Exchange IIS logs for connections lacking proper SSL negotiation

Monitoring Recommendations

• Enable detailed logging for Exchange ActiveSync connections and review for unencrypted session establishments
• Configure SIEM alerts for ActiveSync authentication attempts over non-TLS connections
• Monitor certificate pinning failures and SSL downgrade attempts from mobile devices
• Audit Samsung device ActiveSync configurations across the organization for proper encryption settings

How to Mitigate CVE-2025-58107

Immediate Actions Required

• Enforce TLS 1.2 or higher for all Exchange ActiveSync connections at the server and network level
• Disable legacy ActiveSync protocol versions that may not properly enforce encryption
• Require certificate-based authentication for mobile device access to Exchange
• Implement network segmentation to limit exposure of Exchange server traffic
• Educate users about the risks of connecting mobile devices through untrusted networks

Patch Information

No specific patch information is available in the CVE data. Organizations should consult Microsoft's security advisories and the detailed analysis in the Medium blog post on this ActiveSync vulnerability for the latest guidance. Ensure Exchange Server is updated to the latest cumulative update and security patches.

Workarounds

• Configure Exchange IIS bindings to only allow HTTPS connections for ActiveSync virtual directories
• Deploy a reverse proxy or web application firewall that enforces TLS for all ActiveSync traffic
• Implement conditional access policies requiring device compliance before ActiveSync connections are permitted
• Consider migrating to modern authentication (OAuth 2.0) instead of basic authentication for mobile device access

# Configuration example
# Enforce TLS 1.2 minimum on Exchange Server via registry
# Run in elevated PowerShell on Exchange Server

# Disable older TLS versions
New-Item 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.0\Server' -Force
Set-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.0\Server' -Name 'Enabled' -Value 0 -Type DWord

New-Item 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Server' -Force
Set-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Server' -Name 'Enabled' -Value 0 -Type DWord

# Verify SSL requirement on ActiveSync virtual directory
Get-ActiveSyncVirtualDirectory | Set-ActiveSyncVirtualDirectory -SSLOffloading $false
Get-ActiveSyncVirtualDirectory | Format-List Name,InternalUrl,ExternalUrl,SSLOffloading