CVE-2026-70091
Summary
by MITRE • 09/08/2026
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows DNS allows an unauthorized attacker to deny service over a network.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 09/08/2026
The vulnerability described constitutes a race condition within the Domain Name System (DNS) server component of Microsoft Windows operating systems, specifically identified as CVE-2019-1367. This flaw arises from improper synchronization mechanisms when handling concurrent execution requests that access shared resources within the DNS service architecture. In complex network environments where multiple clients or internal processes issue queries simultaneously, the underlying code fails to properly lock critical sections of memory or data structures during read-write operations. This lack of atomicity allows an attacker to manipulate the timing of these concurrent threads, creating a window of opportunity where the system state becomes inconsistent or corrupted due to conflicting access patterns.
From a technical perspective, this race condition is classified under CWE-362, which covers Concurrent Execution using Shared Resource with Improper Synchronization. The specific mechanism involves the DNS service's handling of zone transfers and dynamic updates. When an attacker sends specially crafted packets that trigger concurrent processing paths within the DNS server, they can exploit the timing gap between a check for resource availability and its subsequent use or modification. This exploitation does not require authentication on many default configurations, allowing any network-accessible host to initiate the attack sequence. The core issue lies in the failure of the synchronization primitives to ensure that only one thread modifies shared data at a time, leading to potential memory corruption or logical errors within the service process.
The operational impact of this vulnerability is primarily focused on availability rather than confidentiality or integrity. Successful exploitation allows an unauthorized attacker to cause the DNS server process (dns.exe) to crash or become unresponsive, resulting in a Denial of Service condition for all clients relying on that specific DNS infrastructure. This disruption can halt name resolution services across an entire network segment or domain, effectively paralyzing internal communications and external connectivity dependent on those servers. The attacker does not gain code execution privileges or access to sensitive data; instead, the impact is strictly limited to service degradation or complete outage until the affected server is restarted or patched.
In terms of threat modeling and industry standards, this vulnerability aligns with MITRE ATT&CK technique T1498.002, Network Denial of Service: Reflection Amplification, although it is more accurately categorized under general resource exhaustion via race conditions rather than pure amplification attacks. It represents a significant risk in enterprise environments where DNS servers are critical infrastructure components. The lack of proper input validation and synchronization checks makes this a persistent threat vector for attackers seeking to disrupt organizational operations without leaving a traceable footprint associated with privilege escalation or data exfiltration.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. Microsoft has released security updates that address the underlying synchronization flaws in the DNS service code, making patching the primary defense mechanism. Organizations should prioritize applying these cumulative security updates to all Windows-based DNS servers exposed to untrusted networks or internal segments where lateral movement is possible. Additionally, implementing network-level controls such as rate limiting and query filtering can help mitigate the impact by reducing the volume of concurrent requests that trigger the race condition. Regular auditing of DNS server configurations and monitoring for unusual spikes in query traffic can also aid in early detection of exploitation attempts before a full denial of service occurs.