Horizon Alert
Summary of the vulnerability and why it matters
This vulnerability involves a flaw in how a specific software component handles data when connecting through an HTTP proxy. If a malicious or compromised server sends specially crafted redirection information, it could potentially allow for the injection of arbitrary headers or requests into the proxy connection. The main concern at this stage is confirming if your environment uses this component in a way that could be exposed.
- Software flaw allows proxy request injection.
- Crucial for verifying potential exposure.
- Confirm relevance and assess impact.
Attack Path
How an attacker could exploit the issue
An attacker could exploit this by tricking a user into connecting to a malicious or compromised RDP server. This server would then send specially crafted data that manipulates the RDP client's connection through an HTTP proxy. The vulnerability lies in how the RDP client handles server-supplied network addresses, allowing the attacker to inject malicious requests into the proxy's communication.
- Entry condition: User connects to a malicious RDP server.
- Trigger point: RDP server sends crafted redirection data.
- Resulting risk: Arbitrary HTTP requests to proxy.
Live Threat
Current exploitation, exposure, and threat context
A malicious RDP server could trick a vulnerable RDP client into sending unintended HTTP requests to a proxy server. This could occur when a client, configured to use an HTTP proxy for RDP connections, connects to a specially crafted RDP server. The server can inject characters into a redirection target, which the client then uses to construct a `CONNECT` request to the proxy.
- HTTP proxy `CONNECT` requests.
- RDP server sends crafted redirection.
- Proxy may process unintended requests.
Operational Fix
Recommended remediation, mitigation, and detection steps
This vulnerability in FreeRDP's handling of RDP redirection addresses requires immediate attention from teams managing remote access infrastructure and the security operations center. The first practical step is to identify all instances of FreeRDP within the environment, determine their exposure to untrusted RDP servers, and confirm which systems are business-critical. Once accountable owners are identified, a remediation plan, potentially involving vendor coordination, can be developed based on the assessed risk.
- Application or infrastructure owners should address.
- Verify FreeRDP presence and exposure.
- Plan for vendor-coordinated updates.
