CVE-2026-96113 in Windows
Summary
by MITRE • 10/14/2026
Heap-based buffer overflow in DNS Server allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability described constitutes a critical security flaw within the Domain Name System (DNS) server infrastructure, specifically manifesting as a heap-based buffer overflow. This type of memory corruption error occurs when data written to a dynamic memory allocation exceeds its allocated boundary, spilling into adjacent memory regions on the heap. In the context of DNS servers, which are fundamental components of internet connectivity responsible for resolving domain names to IP addresses, such vulnerabilities pose an existential threat to network stability and security. The specific nature of this flaw allows an unauthorized attacker, operating remotely over a network connection, to exploit the improper handling of crafted DNS queries or responses. By sending specially constructed packets that trigger the buffer overflow condition, the attacker can overwrite critical memory structures, potentially gaining control over the execution flow of the server process.
From a technical perspective, heap-based buffer overflows are particularly dangerous because they often bypass traditional stack protection mechanisms and allow for more complex exploitation techniques compared to stack-based overflows. The DNS protocol is designed to handle variable-length data fields, such as resource records in query responses or large TXT records. If the server software fails to adequately validate the length of incoming data against the size of the buffer allocated to store it, an attacker can inject shellcode or other malicious payloads into the overflowed memory region. This payload may then be executed when the program attempts to use corrupted pointers or function return addresses that have been overwritten by the attack vector. The ability to execute arbitrary code with the privileges of the DNS service account typically grants the attacker full control over the underlying operating system, enabling them to install backdoors, exfiltrate sensitive data, pivot into other network segments, or launch further attacks against internal assets.
The operational impact of this vulnerability is severe due to the ubiquitous nature of DNS services and their critical role in enterprise and public internet infrastructure. A successful exploitation could lead to a complete compromise of the affected server, resulting in service disruption through denial-of-service conditions if the attacker chooses to destabilize the system rather than maintain persistence. Furthermore, compromised DNS servers can be repurposed for malicious activities such as domain generation algorithm (DGA) based botnet command and control communications, phishing campaigns by resolving legitimate domains to attacker-controlled IPs, or cache poisoning attacks that misdirect users to fraudulent websites. The remote nature of the exploit means that no user interaction is required, allowing automated scanning tools like those found in common vulnerability scanners to rapidly identify and compromise vulnerable systems across large networks.
To mitigate this risk, organizations must prioritize immediate patching of all DNS server software versions known to be susceptible to heap-based buffer overflow vulnerabilities. Vendor-provided updates typically include fixes that enforce strict bounds checking on input data before processing or allocation. In addition to applying patches, network segmentation strategies should be employed to restrict access to DNS servers from untrusted networks, ensuring they are only accessible by authorized resolvers and clients. Implementing ingress filtering rules at the perimeter firewall can help block malformed packets containing oversized fields that trigger the overflow condition. Furthermore, deploying intrusion detection systems with signatures specific to this vulnerability type can provide an additional layer of defense by alerting security operations centers to attempted exploitation activities in real time. Regular auditing of DNS configurations and continuous monitoring for anomalous traffic patterns are also essential components of a robust defense-in-depth strategy against such high-severity remote code execution flaws. This vulnerability aligns with Common Weakness Enumeration identifier CWE-120, which classifies buffer copy without checking size limits, and is often associated with MITRE ATT&CK technique T1190, Exploit Public-Facing Application, highlighting the direct path from external reconnaissance to initial access through a widely deployed service.