Description

Use after free in Microsoft QUIC allows an unauthorized attacker to execute code over a network.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-08-11T17:18:35.320Z",
  "pubdate": "2026-08-11T17:18:35.320Z",
  "executiveSummary": "This vulnerability is classified as a Use After Free (UAF) memory corruption flaw affecting Microsoft QUIC. The security defect arises from improper management of dynamic memory allocation and object lifecycles within the affected network stack component. An unauthorized, remote attacker can leverage this weakness to achieve arbitrary code execution over a network without requiring prior authentication or user interaction.\nThe impact of successful exploitation is critical, potentially granting the adversary full control over the compromised system's execution flow and underlying operating system resources. The risk implications are severe, as Microsoft QUIC handles core network transport functions, exposing internet-facing services and client applications to remote code execution vectors. Exploitation requirements are minimal regarding privileges, as the attack vector relies purely on network-based interaction with the vulnerable service handling QUIC packets. Attackers capable of delivering specifically crafted network payloads can induce deterministic memory corruption conditions, facilitating reliable exploitation of the affected infrastructure.",
  "technicalDetails": "The root cause of the vulnerability resides in the memory management logic of Microsoft QUIC, specifically in how connection contexts, streams, or cryptographic states are deallocated and subsequently referenced. A Use After Free condition occurs when a memory buffer or object is freed, but one or more pointers to that memory persist within the application context. If the program attempts to dereference these dangling pointers, it interacts with reclaimed or unmapped memory, leading to unpredictable behavior, denial of service, or deterministic memory corruption.\nThe vulnerable component is the Microsoft QUIC transport protocol implementation, which exposes network-facing endpoints handling incoming packet streams. The attack flow begins with an unauthorized, remote attacker transmitting maliciously crafted QUIC packets designed to manipulate state transitions and trigger asynchronous operations within the protocol state machine. By inducing a race condition or an improper cleanup sequence during connection teardown, re-keying, or stream resetting, the application releases the memory associated with a specific internal object while maintaining active references to it.\nWhen the application subsequently accesses the dangling pointer, the attacker can influence the contents of the reallocated memory block through heap spraying or heap grooming techniques. If the reclaimed memory is populated with attacker-controlled data containing malicious function pointers or shellcode, the subsequent dereference redirects the instruction pointer to arbitrary locations. The network exposure is direct, as the vulnerability is reachable over the network via standard QUIC communication channels. Authentication and privilege requirements are non-existent, meaning any unauthenticated network peer can initiate the attack sequence against a vulnerable listener.\nThe post-exploitation impact includes arbitrary code execution within the security context of the process utilizing Microsoft QUIC, which often runs with elevated privileges or direct access to network sockets and system resources. This enables threat actors to establish persistence, pivot deeper into internal networks, or execute further system-level compromise payloads."
}