CVE-2026-70330 is a medium severity flaw in Windows DNS in Windows DNS, scored 6.7 by the record. Per the NVD record, it allows an authorized attacker to elevate privileges locally. The record does not state a fixed build, so use the Microsoft advisory for the update that applies to your version and apply it.
What's affected
The NVD record lists these affected products: Windows 10 1607; Windows 10 1809; Windows 10 21h2; Windows 10 22h2; Windows 11 23h2; Windows 11 24h2; Windows 11 25h2; Windows 11 26h1.
The record describes the issue this way: Heap-based buffer overflow in Windows DNS allows an authorized attacker to elevate privileges locally.
The record gives a CVSS 3.1 base score of 6.7 (MEDIUM), published 2026-08-11, with the vector CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. The vector reads as follows. Access is locally, attack complexity is low, and privileges required are high. No user interaction is needed. Scope is unchanged. Confidentiality, integrity and availability impact are high, high and high.
The advisory is the authority on build numbers, and our automated fetch of the Microsoft page returned no advisory text, so this guide stops at what the NVD record states. Where Microsoft's advisory differs from this record on severity or versions, trust the advisory and note the difference in your own tracking.
How to check if you're exposed
Start with the exact Windows build on each machine, then compare it to the fixed build or KB listed in the Microsoft advisory.
winver
Get-ComputerInfo | Select-Object WindowsProductName, OsVersion, OsBuildNumber
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 10
Then check whether the DNS Server role is installed on the machine, which tells you how much of your estate to treat first:
Get-WindowsFeature DNS
Match the output against the advisory's table for your Windows version. If the fixing KB is not in the hotfix list, treat the machine as exposed until you confirm otherwise. For a fleet, run the same query through your endpoint management tool instead of machine by machine.
What to do now
- Read the Microsoft advisory and note the fixing update for each Windows version.
- Patch machines running the DNS Server role first.
- Review who holds high privileges on those servers, since the vector needs them.
- Confirm the new build and record any server that could not be patched.
Why it matters
CWE-122 (heap-based buffer overflow) describes a weakness where data is written past the end of a heap allocation and damages neighboring memory.
Operating system flaws matter because the component runs with high privileges on every machine that has it, and a fleet is slow to patch. The record's own scoring tells you how to rank this one: read the attack vector and privileges lines above, then compare with the machines you actually run.
CVE-2026-70304 and CVE-2026-70330 share a description and score. Check that the update you deploy covers both IDs.
The record's kev field is false, so the record does not list this CVE in CISA's Known Exploited Vulnerabilities catalog, and no fetched advisory said it was exploited. That is a snapshot, not a promise, so keep watching.
Safeguard's Gold page for this CVE tracks the record, and the free in-browser scan can check dependency manifests for related issues. Reachability analysis helps with libraries, though it does not apply to operating system patches.
Quick check
Does this CVE appear in the CISA Known Exploited Vulnerabilities list?
The record's kev field is false, so it is not listed in CISA's catalog as of the record we hold. That can change, so check the catalog if you are prioritizing.
Does the attacker need to be an administrator?
The vector lists high privileges required and local access, so the record describes a post-compromise step rather than a first way in. Patching still closes it.
Sources
- Microsoft Security Update Guide entry for CVE-2026-70330 (the page did not return readable advisory text to our automated fetch, so confirm details there)
- NVD record for CVE-2026-70330 as supplied in the Safeguard batch data
Last reviewed: 18 October 2026.
