CVE-2026-105016 in .NET
Summary
by MITRE • 10/13/2026
Heap-based buffer overflow in Microsoft QUIC allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/13/2026
The vulnerability identified as a heap-based buffer overflow within the Microsoft QUIC implementation represents a critical security flaw that compromises the integrity and availability of systems relying on this protocol for secure, reliable transport layer communication. The Quick UDP Internet Connections (QUIC) protocol is widely adopted by major web browsers and services to enhance performance over TLS 1.3, making any defect in its core library particularly dangerous. In this specific instance, the flaw resides in how the application manages memory allocation on the heap during the processing of incoming network packets. When an attacker sends a specially crafted packet containing malformed data structures or oversized fields, the QUIC stack fails to perform adequate bounds checking before copying the input into a pre-allocated buffer. This lack of validation allows the write operation to exceed the boundaries of the allocated memory region, overwriting adjacent heap metadata or other critical data structures stored in contiguous memory locations.
From a technical perspective, this type of vulnerability is classified under CWE-122, which denotes a heap-based buffer overflow. The exploitation mechanism typically involves manipulating the overwritten memory to alter control flow execution paths. By carefully crafting the payload, an attacker can overwrite function pointers or exception handling structures within the process space. This manipulation enables the injection and subsequent execution of arbitrary machine code with the privileges of the affected application. Since QUIC is often integrated into network-facing services such as web servers, proxies, or API gateways, the attack vector is remote and requires no user interaction beyond establishing a connection to the vulnerable service. The ability to execute code remotely makes this vulnerability a high-severity threat that can lead to full system compromise, including data exfiltration, installation of malware, or establishment of persistent backdoors within the network infrastructure.
The operational impact of exploiting this heap-based buffer overflow extends far beyond simple denial of service scenarios, although crash-induced availability issues are also possible if exploitation attempts fail and cause memory corruption that terminates the process. Successful exploitation allows an unauthorized attacker to gain complete control over the affected system or application instance. This can result in the theft of sensitive data transmitted through QUIC connections, such as authentication tokens, personal identifiable information, or proprietary business logic. Furthermore, because QUIC is frequently used for high-throughput and low-latency communications, a compromised service could be leveraged to pivot into internal network segments, escalating the attack from an external perimeter breach to an insider threat scenario. The persistence of this vulnerability in widely deployed libraries means that any organization utilizing Microsoft's implementation without timely patching remains exposed to automated scanning tools and targeted attacks designed specifically for this flaw.
To mitigate the risks associated with this heap-based buffer overflow, organizations must prioritize immediate remediation through vendor-provided updates. Applying the latest security patches released by Microsoft ensures that the underlying memory management routines in the QUIC library are corrected to include proper bounds checking and input validation mechanisms. In environments where patching is not immediately feasible due to compatibility constraints or operational downtime requirements, network-level mitigations should be implemented as a compensatory control. This includes deploying Web Application Firewalls (WAFs) or intrusion prevention systems configured with signatures capable of detecting anomalous QUIC packet structures that trigger the overflow condition. Additionally, restricting access to services utilizing QUIC through strict firewall rules and zero-trust architecture principles can limit the attack surface by ensuring only authorized IP addresses can initiate connections. Regular vulnerability scanning and continuous monitoring for exploitation attempts are also essential components of a defense-in-depth strategy against such critical remote code execution vulnerabilities.