Critical Heap-Based Buffer Overflow in Windows RRAS: Analyzing CVE-2025-49657
Introduction
A newly disclosed critical vulnerability, CVE-2025-49657, has emerged in Microsoft's Routing and Remote Access Service (RRAS), posing severe risks of remote code execution without authentication. This heap-based buffer overflow flaw, rated 8.8 on the CVSS scale, allows attackers to compromise Windows systems remotely, potentially leading to complete system takeover.
Technical Information
The vulnerability resides within the Windows Routing and Remote Access Service (RRAS), a critical component responsible for routing, VPN services, and remote access management. Specifically, the flaw arises from improper handling of heap memory during the processing of network packets. RRAS fails to adequately validate the size of incoming packets, leading to a heap-based buffer overflow when oversized packets are processed.
Attackers exploit this vulnerability by crafting malicious network packets exceeding the allocated buffer size, targeting UDP ports 1812, 1813 (RADIUS), and TCP port 1701 (L2TP). Upon receiving these packets, RRAS improperly copies the data into heap memory without proper bounds checking, causing memory corruption. This corruption can overwrite adjacent memory structures, including function pointers and exception handlers, allowing attackers to execute arbitrary code with SYSTEM-level privileges.
This attack vector requires no authentication or user interaction, significantly increasing its potential impact. Systems running RRAS services exposed to untrusted networks, especially internet-facing servers, are particularly vulnerable.
Patch Information
Microsoft has addressed the heap-based buffer overflow vulnerability in the Windows Routing and Remote Access Service (RRAS) by releasing a security update as part of their July 2025 Patch Tuesday. This update modifies how RRAS handles memory operations to prevent unauthorized code execution over a network. Administrators are strongly advised to apply this update promptly to mitigate potential risks associated with this vulnerability.
Affected Systems and Versions
The vulnerability affects Windows operating systems with RRAS enabled, including:
- Windows Server 2012 R2
- Windows Server 2016
- Windows Server 2019
- Windows Server 2022
- Windows 10 (all versions with RRAS enabled)
- Windows 11 (all versions with RRAS enabled)
Systems configured as VPN servers, routers, or utilizing DirectAccess with RRAS components are specifically vulnerable.
Vendor Security History
Microsoft regularly encounters vulnerabilities in legacy components such as RRAS, reflecting ongoing challenges in securing complex software ecosystems. Historically, Microsoft has demonstrated a consistent and timely response to critical vulnerabilities through their monthly Patch Tuesday updates, maintaining a robust security posture and proactive vulnerability management practices.
References
Source: This report was created using AI
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