CVE-2026-97839 in Windows
Summary
by MITRE • 10/14/2026
Out-of-bounds read in DNS Server allows an authorized attacker to disclose information over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described constitutes a critical security flaw within the Domain Name System (DNS) server infrastructure, specifically categorized as an out-of-bounds read condition. This type of memory safety error occurs when the software attempts to access data at a memory location that is outside the boundaries of the intended buffer or array structure. In the context of DNS servers, which are fundamental components of internet routing and resolution services, such flaws can have severe implications for system integrity and confidentiality. The root cause typically stems from insufficient validation of input parameters or improper handling of packet structures received during query processing. When a malformed or specially crafted DNS request is processed by the vulnerable server component, it triggers an illegal memory access operation where the application reads data beyond the allocated buffer limits.
From a technical perspective, this flaw aligns with Common Weakness Enumeration (CWE) identifiers such as CWE-125 Out-of-bounds Read and potentially CWE-20 Improper Input Validation if the underlying issue involves failure to sanitize or verify incoming network packets before processing. The operational mechanism relies on the DNS server's need to parse complex query structures, including variable-length fields like domain names and resource records. If the logic governing these parses fails to correctly calculate buffer boundaries based on actual packet content length versus expected structure size, it may read adjacent memory contents. This behavior does not necessarily lead to immediate code execution but serves as a potent information disclosure vector, allowing an attacker to extract sensitive data residing in the server's memory space that was not intended for public exposure.
The impact of this vulnerability is primarily centered on confidentiality and potentially availability depending on how the system handles subsequent errors after the illegal read operation. An authorized attacker, possessing valid credentials or access privileges within the network segment where the DNS server resides, can exploit this flaw to leak internal information. This disclosed data might include memory dumps containing cached DNS records, authentication tokens, cryptographic keys, or other proprietary business logic stored in adjacent memory blocks. Such leakage facilitates further reconnaissance efforts by adversaries who can use the extracted intelligence to map internal networks, identify high-value targets, or craft more sophisticated attacks against connected systems. The ability of an authorized actor to perform this action underscores a significant risk within environments where privilege separation is not strictly enforced between different user roles interacting with DNS services.
In terms of threat modeling and adversary behavior, this vulnerability maps directly to the MITRE ATT&CK framework technique T1005 Data from Local System which describes data staged in local access locations for later exfiltration or immediate use during an incident response evasion scenario. Although the initial action is a read operation rather than explicit staging, the outcome aligns with gathering system information that aids subsequent phases of intrusion such as credential dumping or lateral movement planning. The presence of authorization requirements indicates that this is not an unauthenticated remote code execution vector but rather represents a privilege escalation pathway where lower-privileged users can gain higher-level insights into server internals through memory corruption techniques.
Mitigation strategies must address both the immediate technical flaw and broader architectural controls to prevent exploitation. Immediate remediation involves applying vendor-provided patches or updates that correct the buffer boundary checks within the DNS service software, ensuring all input lengths are validated against allocated memory sizes before any read operations occur. Security teams should also implement network segmentation policies to restrict access to DNS servers only from authorized management stations and trusted resolvers, thereby limiting the attack surface available to potential insiders or compromised low-privilege accounts. Additionally, deploying intrusion detection systems configured with signatures for anomalous DNS packet structures can help identify attempted exploitation in real-time. Regular auditing of user permissions associated with DNS administration tools ensures that fewer individuals possess the necessary access rights to trigger such vulnerabilities, reducing the overall risk profile significantly while waiting for permanent code fixes to be deployed across all affected infrastructure components.