CVE-2025-49757: Critical Buffer Overflow Vulnerability in Windows RRAS

Overview

The Common Vulnerabilities and Exposures (CVE) system has identified a critical vulnerability, CVE-2025-49757, that can have severe implications for systems running the Windows Routing and Remote Access Service (RRAS). This heap-based buffer overflow vulnerability allows unauthorized attackers to execute arbitrary code remotely over a network, potentially leading to system compromise or data leakage. This vulnerability is a significant concern due to its high severity rating and the widespread usage of Windows RRAS in enterprise environments, making urgent mitigation a necessity.

Vulnerability Summary

CVE ID: CVE-2025-49757
Severity: High (8.8 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System Compromise, Data Leakage

Affected Products

Product | Affected Versions

Windows Routing and Remote Access Service (RRAS) | All versions before the patch

How the Exploit Works

The exploit leverages a heap-based buffer overflow vulnerability in Windows RRAS. In essence, an attacker can send specially crafted packets to the vulnerable service, causing it to overflow its buffer, a temporary storage area. The overflow can overwrite other portions of the memory, changing the application’s behavior. In this case, the overflow allows the attacker to execute arbitrary code on the system, potentially leading to system compromise or data leakage.

Conceptual Example Code

Here’s a conceptual example of how the vulnerability might be exploited with a malicious payload. Note that this is a generalized representation and not an actual exploit code:

POST /RRAS/endpoint HTTP/1.1
Host: target.example.com
Content-Type: application/octet-stream
{ "malicious_payload": "BUFFER_OVERFLOW_TRIGGERING_CODE" }

In this example, the attacker sends a POST request to the RRAS endpoint of the target system. The malicious payload contains the code that triggers the buffer overflow, leading to the execution of arbitrary code.

Mitigation Guidance

Microsoft has released a patch to address this vulnerability, and users are advised to apply it immediately to their systems. If immediate patching is not feasible, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can be used as temporary mitigation, configured to detect and block attempts to exploit this vulnerability.
However, these temporary measures do not eliminate the vulnerability and only reduce the risk of exploitation. Therefore, they should be used as a stopgap measure until the patch can be applied. Users should also consider additional security measures such as network segmentation and least privileges policies to minimize potential damage from future vulnerabilities.