CVE-2025-49673 in Windows
Summary
by MITRE • 07/08/2025
Heap-based buffer overflow in Windows Routing and Remote Access Service (RRAS) allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 08/20/2026
The vulnerability identified as a heap-based buffer overflow within the Microsoft Windows Routing and Remote Access Service, commonly referred to as RRAS, represents a critical security flaw that compromises the integrity of remote access infrastructure. This service is fundamental for organizations requiring secure remote connectivity, managing dial-up connections, or configuring network address translation across diverse network interfaces. The specific nature of this vulnerability lies in how RRAS handles incoming data packets during routing operations. When processing certain malformed or specially crafted network traffic, the application fails to adequately validate buffer boundaries before writing data to memory locations allocated on the heap. This lack of rigorous input validation allows an attacker to write beyond the intended limits of a designated memory block, corrupting adjacent heap metadata and potentially overwriting critical control structures such as function pointers or exception handlers.
From a technical perspective, this flaw aligns with Common Weakness Enumeration category CWE-122, which describes a heap-based buffer overflow where data is written past the end of an allocated region on the heap rather than the stack. The operational impact of exploiting this vulnerability is severe because it enables arbitrary code execution under the context of the affected service account. Since RRAS typically runs with high privileges to manage network configurations and routing tables, successful exploitation grants an unauthorized attacker full control over the underlying operating system. This access can be leveraged to install malware, create new user accounts for persistent backdoor access, or manipulate network traffic interception mechanisms. The attack vector is remote, meaning that a non-authenticated adversary located on the same local area network segment or accessible via routed networks can trigger this condition without needing prior credentials, significantly expanding the potential blast radius of the exploit.
The exploitation mechanism often involves crafting specific packet headers or payload structures that force RRAS to allocate memory buffers and subsequently write data in an uncontrolled manner. By carefully manipulating heap layout through repeated allocations and deallocations, known as heap grooming techniques, an attacker can position their malicious shellcode adjacent to corrupted metadata. When the system attempts to free these blocks or invoke function pointers associated with them, it redirects execution flow to the attacker-controlled memory region. This process is consistent with attack patterns observed in MITRE ATT&CK framework technique T1203, which covers exploitation for client execution, particularly when targeting services that handle network traffic processing. The ability to execute code remotely makes this vulnerability a prime candidate for automated worm propagation or targeted attacks against critical infrastructure components such as firewalls and routers running Windows Server operating systems.
Mitigation strategies must address both immediate remediation and long-term architectural resilience. The primary defense is the timely application of security patches provided by Microsoft, which include fixes to validate buffer sizes and enforce stricter bounds checking within RRAS code paths. Organizations should prioritize patching all exposed servers hosting the Routing and Remote Access role until updates are deployed. In environments where immediate patching is not feasible due to operational constraints, network segmentation becomes crucial. Restricting access to RRAS ports using firewall rules ensures that only trusted IP addresses can communicate with the service, thereby reducing the attack surface available to potential adversaries. Additionally, enabling advanced logging and monitoring for unusual routing table changes or unexpected process creations on affected systems can aid in early detection of exploitation attempts. Regular audits of network configurations and disabling unused services further reduce the likelihood of successful compromise by minimizing the presence of vulnerable components within the enterprise perimeter.