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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain low-privilege network access to DNS server
  2. Exploit
    Send crafted DNS request
  3. Execution
    Trigger out-of-bounds read in parser
  4. Impact
    Receive leaked adjacent memory in response

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 attacker to already hold low-level authorization on or toward the target (CVSS PR:L), so this is not an anonymous internet-wide attack despite the network vector. The vulnerable component is the Windows DNS Server role, meaning only hosts running that role (domain controllers and dedicated DNS servers) are affected - workstations and servers without the DNS role are out of scope. The flaw is an out-of-bounds read reachable over the network with low complexity and no user interaction, yielding memory disclosure only (no integrity or availability impact). Limiting factors: the required authorization level and the need for the DNS Server role to be installed and reachable; Microsoft's description does not name the specific record type or query feature that triggers the read.

Impact

This is a moderate-priority vulnerability, not a drop-everything emergency. The CVSS 3.1 base score of 6.5 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N) reflects a network-reachable, low-complexity information-disclosure flaw that nonetheless requires some level of authorization (PR:L), which meaningfully caps the exploit population versus a fully unauthenticated bug. The impact profile is confidentiality-only (C:H, I:N, A:N): memory contents can leak, but the attacker cannot modify data or crash the service through this issue alone. No EPSS score, SSVC decision, KEV listing, or POC was provided in the input, so exploitation likelihood cannot be quantified - per precision rules this is treated as 'no public exploit identified at time of analysis.' There is no conflict between the CVSS vector and the description: both agree on a network-facing, authorized-attacker, information-disclosure scenario. Realistic risk is elevated by the product - Windows DNS Server is a widely deployed infrastructure role - but tempered by the authorization requirement and the absence of any evidence of active exploitation. Treat as a standard patch-cycle item, prioritizing internet-facing or multi-tenant DNS servers where low-privilege access is more plausible.

Exploit ScenarioDerived

An attacker with low-level authorized access to a Windows DNS Server sends a specially crafted query or request that causes the service to read beyond an allocated buffer (CWE-125), returning adjacent process memory in the response. Because the attack vector is network-based with low complexity (AV:N/AC:L), this can be performed remotely once the attacker holds the required privileges, potentially leaking sensitive in-memory data such as cached records or other process state. No public exploit code was identified in the provided data.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.7% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 13, 2026

An out-of-bounds read in the Windows DNS Server role allows an attacker who already holds low-level authorization on or toward the target to read beyond the bounds of an allocated buffer and disclose server memory over the network (CVSS 6.5, CWE-125, PR:L). Only hosts running the DNS Server role are in scope - domain controllers and dedicated DNS servers on Windows Server 2012 through 2025 and supported Windows 10/11 builds - so the network vector does not translate into an anonymous internet-wide attack. Microsoft has published vendor updates for the affected builds, and no public exploit identified at time of analysis; impact is confidentiality-only, with no integrity or availability effect.

RemediationAI

Patch available per vendor advisory: Microsoft has released security updates for CVE-2026-97840 through the MSRC Security Update Guide (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-97840), with fixed builds corresponding to the upper bounds of the affected ranges above - for example 10.0.20348.5761 for Windows Server 2022, 10.0.17763.9376 for Windows Server 2019, 10.0.14393.9612 for Windows Server 2016, 10.0.26100.9711 / 10.0.26100.33650 for Windows 11 24H2 and Windows Server 2025, 10.0.22631.7652 for Windows 11 23H2, and 6.3.9600.23470 / 6.2.9200.26434 for the legacy Server 2012 R2 and 2012 branches. Apply the monthly cumulative update that carries the corrected DNS Server binaries and plan a restart of the DNS Server service or a reboot for domain controllers; verify the resulting build number matches or exceeds the fixed build for each SKU. Because exploitation requires low-level authorization, the highest-value compensating control while patching is to restrict who can reach the DNS service: firewall TCP/UDP port 53 so that only trusted resolvers, forwarders, and client subnets can query the server, and block direct external or cross-VLAN access to DNS Server instances - the trade-off is that misconfigured allow-lists can break legitimate resolution for roaming clients or partner networks. Where the server does not require it, disable recursion and open resolution to reduce the query surface, and remove or disable the DNS Server role from any host that does not genuinely need it, accepting that this may not be feasible for domain controllers holding the AD-integrated DNS zones. Enabling DNS query logging and monitoring for anomalous or malformed query patterns gives detection coverage but adds log volume and I/O on busy resolvers. As no public exploit code is known at time of analysis, these controls are precautionary hardening rather than incident response, and they do not substitute for applying the vendor update.

Affected VersionsENISA

Windows 11 Version 24H2 10.0.26100.0 <10.0.26100.9711
Windows Server 2019 (Server Core installation) 10.0.17763.0 <10.0.17763.9376
Windows Server 2016 10.0.14393.0 <10.0.14393.9612
Windows Server 2025 10.0.26100.0 <10.0.26100.33650
Windows 11 Version 25H2 10.0.26200.0 <10.0.26200.9711
Windows 10 Version 22H2 10.0.19045.0 <10.0.19044.7807
Windows Server 2012 R2 (Server Core installation) 6.3.9600.0 <6.3.9600.23470
Windows Server 2016 (Server Core installation) 10.0.14393.0 <10.0.14393.9612
Windows Server 2025 (Server Core installation) 10.0.26100.0 <10.0.26100.33650
Windows 10 Version 1809 10.0.17763.0 <10.0.17763.9376
Windows 10 Version 21H2 10.0.19044.0 <10.0.19044.7807
Windows Server 2022 10.0.20348.0 <10.0.20348.5761
Windows 11 Version 23H2 10.0.22631.0 <10.0.22631.7652
Windows Server 2012 (Server Core installation) 6.2.9200.0 <6.2.9200.26434
Windows 11 version 26H1 10.0.28000.0 <10.0.28000.3231
Windows 10 Version 1607 10.0.14393.0 <10.0.14393.9612
Windows Server 2012 6.2.9200.0 <6.2.9200.26434
Windows Server 2019 10.0.17763.0 <10.0.17763.9376
Windows 11 Version 26H2 10.0.26300.0 <10.0.26300.9711
Windows Server 2012 R2 6.3.9600.0 <6.3.9600.23470

Affected Packages

euvd windows_10_version_1607 fix: 10.0.14393.9612
euvd windows_10_version_1809 fix: 10.0.17763.9376
euvd windows_10_version_21h2 fix: 10.0.19044.7807
euvd windows_10_version_22h2 fix: 10.0.19044.7807
euvd windows_11_version_23h2 fix: 10.0.22631.7652
euvd windows_11_version_24h2 fix: 10.0.26100.9711
euvd windows_11_version_25h2 fix: 10.0.26200.9711
euvd windows_11_version_26h1 fix: 10.0.28000.3231
euvd windows_11_version_26h2 fix: 10.0.26300.9711
euvd windows_server_2012 fix: 6.2.9200.26434
euvd windows_server_2012_r2 fix: 6.3.9600.23470
euvd windows_server_2012_r2_server_core_installation fix: 6.3.9600.23470
euvd windows_server_2012_server_core_installation fix: 6.2.9200.26434
euvd windows_server_2016 fix: 10.0.14393.9612
euvd windows_server_2016_server_core_installation fix: 10.0.14393.9612
euvd windows_server_2019 fix: 10.0.17763.9376
euvd windows_server_2019_server_core_installation fix: 10.0.17763.9376
euvd windows_server_2022 fix: 10.0.20348.5761
euvd windows_server_2025 fix: 10.0.26100.33650
euvd windows_server_2025_server_core_installation fix: 10.0.26100.33650

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

The flaw is an out-of-bounds read (CWE-125) inside the Windows DNS Server service, a core Windows role that parses inbound queries and resource records across UDP/TCP port 53 and typically runs with high privileges on domain controllers. CWE-125 covers cases where a parser trusts a length, offset, or index derived from attacker-influenced input and reads past the end of a heap or stack buffer; per the description a malicious or malformed DNS interaction causes the service to return or otherwise expose adjacent memory contents. The distinguishing characteristic here is disclosure rather than corruption - the CVSS vector AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N indicates low-complexity network reachability with no user interaction, but explicitly requires the attacker to already possess low-level authorization (PR:L), and produces no integrity or availability impact. Tags associated with this CVE include Buffer Overflow and Information Disclosure, consistent with a bounds-checking failure in a memory-unsafe parser. Microsoft has not publicly named the specific record type, EDNS option, or query feature that triggers the over-read, so defenders cannot precisely scope exposure by query shape and should treat all DNS Server role instances as potentially affected until patched. Because the information disclosed is DNS process memory, a successful attacker could obtain internal data such as cached records, configuration details, or credential-adjacent material present in the process address space, making this a useful reconnaissance or lateral-movement primitive when chained with other weaknesses, even though it is not remotely exploitable without some level of prior access.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 6.5 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
vuln.today AI 6.5 MEDIUM

Network-reachable DNS service (AV:N, AC:L) but the 'authorized attacker' wording and info-disclosure-only nature justify PR:L and C:H with I:N/A:N.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Lifecycle Timeline

2
Patch available
Oct 13, 2026 - 20:20 EUVD
CVE Published
Oct 13, 2026 - 19:22 nvd
MEDIUM 6.5

DescriptionCVE.org

Out-of-bounds read in DNS Server allows an authorized attacker to disclose information over a network.

Threat Intelligence Overview

EPSS Score
0.7%
Top 47% exploitable
Prevalence
High
DNS Server role ships across all supported Windows Server editions
Vendor Status
Publicly Disclosed:No
Exploited:No
Latest Software Release:Exploitation Less Likely
Data Quality
5 sources
Confidence: Medium

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.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.7%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

33
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +32
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

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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