EUVD-2026-100438
GHSA-h433-fh6x-hv2x
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessObtain low-level network access to DNS server
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DeliverySend crafted DNS query data
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ExploitTrigger out-of-bounds read in parser
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ExecutionReceive leaked process memory
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ImpactHarvest disclosed sensitive information
Vulnerability Assessment
| Weakness |
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, read limits
MITRE ATT&CK
1 technique across 1 tactic: Collection The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Exploitation requires the target host to have the Windows DNS Server role installed and running (a role-specific, not default-workstation, condition) and network reachability to that service. The CVSS vector PR:L means the attacker must hold low-level privileges / authentication rather than being fully anonymous, which limits opportunistic mass exploitation; no user interaction is needed (UI:N) and attack complexity is low (AC:L). Impact is limited to confidentiality (information disclosure) - the flaw cannot modify data or crash the service (I:N/A:N). Affected builds are enumerated per EUVD-2026-100438; systems patched to the listed fixed build numbers (e.g. Server 2025 ≥10.0.26100.33650, Server 2019 ≥10.0.17763.9376) are not exposed. |
| Impact | This is a moderate-severity information-disclosure flaw (CVSS 6.5) in the Windows DNS Server role. The CVSS vector (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N) indicates a network-reachable, low-complexity attack requiring low-level privileges (PR:L = authenticated) with no user interaction, yielding high confidentiality impact but no integrity or availability impact - consistent with an out-of-bounds read (CWE-125) that leaks process memory. No EPSS score, SSVC decision, KEV listing, or POC is present in the supplied data, so there is no signal of active or probable near-term exploitation; the only exploitation-relevant signal is that Microsoft (the reporter, secure@microsoft.com) has shipped patches across all affected Windows builds. The PR:L requirement meaningfully lowers real-world risk versus an unauthenticated DNS bug, and the impact is read-only disclosure rather than code execution or service disruption. Net assessment: a genuine but second-tier priority - patch in normal cycle, prioritized higher where DNS servers are internet-facing or hold sensitive co-located memory. Note one tension to verify with the vendor: C:H for an OOB read is on the high end and the actual quantity/sensitivity of disclosed memory is not described, so the confidentiality rating may overstate practical impact. |
| Exploit ScenarioDerived | An attacker with low-level authenticated access to a network path reaching a vulnerable Windows DNS Server sends specially crafted DNS queries or data that trigger an out-of-bounds read in the server's parsing logic. The server responds in a way that leaks adjacent process memory, potentially exposing sensitive in-memory data over the network. No public exploit code is identified in the available data, and exploitation requires at least low-level privileges (PR:L). |
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Alert meAnalysisAIv1 – Oct 13, 2026
Out-of-bounds read in the Microsoft Windows DNS Server role lets an authenticated, low-privileged attacker reachable over the network read past the end of a buffer and disclose information from server memory, rated CVSS 6.5 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N). The flaw affects a broad set of Windows client and server builds running the DNS Server role, enumerated by EUVD-2026-100438, and exposure is limited to confidentiality - integrity and availability are unaffected and no user interaction is required. There is no CISA KEV listing and no public exploit identified at time of analysis; the PR:L vector means the attacker must already hold low-level credentials, which constrains opportunistic mass exploitation, and vendor patches are available.
RemediationAI
Vendor-released patch: apply the Microsoft update for CVE-2026-97837 from the MSRC update guide (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-97837); fixed builds per EUVD-2026-100438 are Windows Server 2025 10.0.26100.33650 or later, Windows Server 2022 10.0.20348.5761 or later, Windows Server 2019 10.0.17763.9376 or later, Windows Server 2016 10.0.14393.9612 or later, Windows Server 2012 R2 6.3.9600.23470 or later, Windows Server 2012 6.2.9200.26434 or later, Windows 11 24H2/25H2 10.0.26100.9711 / 10.0.26200.9711 or later, Windows 11 26H2 10.0.26300.9711 or later, Windows 11 26H1 10.0.28000.3231 or later, Windows 11 23H2 10.0.22631.7652 or later, Windows 10 22H2/21H2 10.0.19044.7807 or later, Windows 10 1809 10.0.17763.9376 or later, and Windows 10 1607 10.0.14393.9612 or later. If the DNS Server role is present but cannot be patched immediately, reduce exposure by blocking inbound UDP/TCP 53 from untrusted networks at the perimeter and host firewall so only authorized resolvers and management subnets can query the service - the trade-off is that any legitimate off-subnet client or zone-transfer peer loses name resolution until the rule is scoped correctly. Where the DNS Server role is not actually required (common on workstations and non-resolver servers), uninstalling or disabling the role removes the attack surface entirely, at the cost of losing local caching/forwarding behavior. Because exploitation requires low-level credentials against the DNS service, tightening who can reach port 53 and auditing accounts with network access to DNS infrastructure is a meaningful compensating control.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 20 packages in euvd
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This is a CWE-125 out-of-bounds read in the Windows DNS Server role - a class of memory-safety defect where the service parses or indexes beyond the bounds of an allocated buffer and returns or leaks adjacent memory contents rather than crashing. Because the vector is AV:N/AC:L with no user interaction, the vulnerable code path is reachable through ordinary DNS request handling on the network, and because PR:L applies, the attacker must possess low-level privileges or authentication rather than being fully anonymous. The impact is pure information disclosure (C:H, I:N, A:N): the defect does not permit data modification or denial of service, so the realistic risk is leakage of server memory that could include configuration details, cached records, or other data useful for follow-on attacks. CPE/version data from EUVD-2026-100438 ties the issue to specific Windows 10, Windows 11 and Windows Server builds across the 1607 through 26H2 update channels, including Server Core installations, confirming the DNS Server role - a role-specific, non-default condition on workstations - is the affected component.
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Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Network-reachable DNS service (AV:N), low complexity (AC:L), requires low-level authentication per vendor (PR:L); read-only memory disclosure gives C:H with no integrity or availability impact.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Out-of-bounds read in DNS Server allows an authorized attacker to disclose information over a network.
Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.
Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
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