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CVE-2026-70330 is a heap-based buffer overflow vulnerability identified in the Windows DNS component. This flaw enables an authorized attacker to elevate privileges locally on an affected system. The vulnerability stems from improper handling of memory allocation within the Windows DNS service, where a specially crafted operation can trigger a buffer overflow in the heap memory space.
The Windows DNS service processes various network requests and responses. When this service encounters a maliciously crafted DNS response or a specific sequence of operations, it fails to properly validate the size of data being written to heap-allocated buffers. This leads to memory corruption, as data exceeds the allocated buffer boundaries and overwrites adjacent memory regions.
An attacker exploiting this vulnerability must first obtain authorized access to the target system, as the attack vector is local. This means the attacker needs valid credentials or some level of existing access to the machine. However, successful exploitation results in a complete compromise of the system’s security boundaries, allowing the attacker to execute arbitrary code with elevated privileges.
The vulnerability is categorized under CWE-122 (Heap-based Buffer Overflow), highlighting the root cause as a memory safety issue. Microsoft Corporation published the vulnerability on August 11, 2026, with the NVD last modifying the entry on August 18, 2026.
Microsoft’s CVSS v3.1 scoring places this vulnerability at 6.7 MEDIUM, with the vector string CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. The NIST NVD assessment provides a more severe rating of 7.8 HIGH using the vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. This discrepancy arises from different assumptions about the privileges required (High vs. Low).
DailyCVE Form:
Platform: Windows DNS
Version: 10.0.14393.0–10.0.14393.9417,
10.0.17763.0–10.0.17763.9120,
10.0.19044.0–10.0.19044.7662,
10.0.19045.0–10.0.19045.7662,
10.0.22631.0–10.0.22631.7516,
10.0.26100.0–before fixed
Vulnerability : Heap-based Buffer Overflow
Severity: 6.7 MEDIUM
date: 08/11/2026
Prediction: September 2026 Patch Tuesday
What Undercode Say:
Analytics indicate that while this vulnerability requires local access, its potential for privilege escalation makes it a significant threat in environments where attackers have already achieved low-level access. The presence of both Microsoft’s and NIST’s CVSS scores suggests some disagreement on the exact prerequisites for exploitation, but both agree on the high impact to confidentiality, integrity, and availability.
Check if system is vulnerable by verifying Windows DNS version systeminfo | findstr /B /C:"OS Name" /C:"OS Version" Query the specific build number to compare against known vulnerable versions wmic os get buildnumber Check DNS service status and configuration sc query dnscache sc query dns Review DNS event logs for potential indicators of exploitation wevtutil qe System /c:5 /f:text /q:"[System[Provider[@Name='Microsoft-Windows-DNS-Client']]]"
Exploit: (Educational Purposes!)
Exploitation of this vulnerability requires an authenticated user to execute a specially crafted application or script that interacts with the Windows DNS service in a way that triggers the heap buffer overflow. The attacker crafts input data that exceeds the expected buffer size, overwriting adjacent heap metadata or function pointers. This memory corruption can be leveraged to redirect execution flow and execute arbitrary shellcode with elevated SYSTEM privileges. Successful exploitation does not require user interaction but does require the attacker to have existing local access and the ability to run code on the target system.
Protection:
- Apply the official security update from Microsoft as soon as it becomes available.
- Restrict local access to systems by enforcing the principle of least privilege.
- Monitor DNS-related event logs for unusual activity or errors that may indicate attempted exploitation.
- Employ endpoint detection and response (EDR) solutions to detect and block memory corruption attacks.
- Disable the DNS Client service if not strictly required in the environment, though this may impact network functionality.
Impact:
Successful exploitation of CVE-2026-70330 allows an attacker to elevate privileges from a low-privileged user account to SYSTEM-level access. This grants the attacker complete control over the affected Windows system, including the ability to install programs, view, change, or delete data, and create new accounts with full user rights. The vulnerability impacts multiple versions of Windows 10 and Windows 11 across x86, x64, and ARM64 architectures. Organizations with unpatched systems face the risk of internal attackers or malware leveraging this flaw to achieve full system compromise.
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Sources:
Reported By: nvd.nist.gov
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