CVE-2015-0016: Microsoft Windows TS WebProxy Directory Traversal Vulnerability

CVE-2015-0016 is a directory traversal vulnerability in the TS WebProxy (TSWbPrxy) component of Microsoft Windows. It allows remote attackers to escalate privileges by abusing how the component handles path references. For IT and security teams, this matters because privilege escalation on Windows hosts can turn limited access into broader control of systems that often hold credentials, sessions, or sensitive data. Confirm exact product scope and fixed builds against the vendor advisory before acting.

How it works

This issue falls under CWE-22 (improper limitation of a pathname to a restricted directory). Directory traversal flaws occur when software accepts attacker-controlled input that includes path elements such as parent-directory references and fails to normalize or constrain them to an intended location. In the TS WebProxy component, a remote attacker can supply crafted input that causes the service to resolve paths outside the expected directory boundary. Successful abuse can lead to privilege escalation on the affected Windows system. Public detail on exact request formats or preconditions is limited; treat any exploitation claims as needing validation against the vendor advisory and your own telemetry rather than assuming a specific attack chain.

Am I affected? How to find it in your systems

TS WebProxy is part of Microsoft Windows Remote Desktop / Terminal Services web-related functionality and typically appears on systems that expose or proxy Remote Desktop web access components. Inventory Windows hosts that run Remote Desktop Services, RD Web Access, or related proxy roles. Check installed Windows versions and update levels against the vendor advisory for CVE-2015-0016; do not rely on generic version ranges. Look for the presence of TSWbPrxy-related binaries or services in standard system directories and confirm whether the component is enabled or reachable from untrusted networks.

• Use asset inventory, SCCM/Intune, or vulnerability scanners that map Microsoft security bulletins to installed builds.
• Review configuration for RD Gateway, RD Web Access, or similar roles that may load the TS WebProxy component.
• Examine web and system logs for anomalous path strings containing traversal sequences directed at TS WebProxy endpoints; correlate with unexpected privilege changes or process creations under elevated contexts.
• Confirm exposure by checking whether the relevant listeners are reachable from outside trusted management networks.

How to remediate

Apply the security updates Microsoft released for this vulnerability, following the vendor instructions referenced in the advisory for CVE-2015-0016. Patching is the primary remediation. After installing updates, reboot if required by the package and verify the component is at the fixed level via your patch-management console or by checking file versions against the advisory.

• Prioritize internet-facing or multi-user Terminal Services hosts.
• Validate that the update supersedes any earlier cumulative packages that may not fully address the issue.
• As hardening for this class of flaw, ensure path canonicalization and least-privilege service accounts are in place for any remaining web-proxy or RD components, and disable unused Remote Desktop web features.

If you can't patch immediately

Reduce attack surface until the vendor update can be deployed. Segment hosts running TS WebProxy or RD Web roles so they are not reachable from untrusted networks. Restrict access to the relevant ports and URLs with network ACLs or host firewalls limited to known management and user subnets. If a web application firewall or reverse proxy sits in front of the service, consider rules that block path-traversal patterns in requests targeting the component; treat this as temporary virtual patching only. Disable the TS WebProxy or associated RD Web features if they are not required for business operations. Increase monitoring for privilege-escalation indicators and anomalous file-system access under the service identity until patches are applied.

If your data may have been exposed

Actively exploited privilege-escalation vulnerabilities can lead to broader compromise and data exposure even when ransomware use is not documented for this CVE. If you suspect successful abuse, isolate affected hosts, preserve logs, and begin incident response focused on credential and lateral-movement checks. You can run a free exposure scan of your email addresses against known breach data to see whether associated accounts appear in prior incidents while you complete containment and patching.