CVE-2026-97841: DNS Server Information Disclosure Vulnerability

CVE-2026-97841 Overview

CVE-2026-97841 is an out-of-bounds read vulnerability in Microsoft DNS Server. An authorized attacker can exploit the flaw over a network to disclose sensitive information from server memory. The weakness is classified under [CWE-125] (Out-of-bounds Read) and affects the confidentiality of data processed by the DNS Server service.

The vulnerability requires low privileges and no user interaction. Successful exploitation does not modify data or disrupt service availability, but it can expose memory contents that may include sensitive configuration or operational data useful for follow-on attacks.

Critical Impact
An authenticated remote attacker can read beyond allocated memory boundaries in the DNS Server component, resulting in disclosure of in-process memory over the network.

Affected Products

Microsoft DNS Server (see the Microsoft Security Update CVE-2026-97841 advisory for the authoritative list of affected builds)

Discovery Timeline

2026-10-13 - CVE CVE-2026-97841 published to NVD
2026-10-13 - Last updated in NVD database

Technical Details for CVE-2026-97841

Vulnerability Analysis

The vulnerability resides in the Microsoft DNS Server service and stems from an out-of-bounds read condition. When the service parses a specially crafted request, it reads memory beyond the intended buffer boundary. The returned data can include adjacent process memory that was never meant to be exposed to the requester.

Exploitation requires network reachability to the DNS Server and valid credentials with low privileges. The attacker does not need to interact with a user, and the attack complexity is low. The scope remains unchanged, meaning the disclosure is limited to the DNS Server process itself.

Root Cause

The root cause is improper validation of a length or index value prior to reading from a buffer. The DNS Server trusts an attacker-influenced field during request processing and reads past the end of an allocated structure. This behavior matches the pattern described by [CWE-125], where read operations exceed the intended boundary of a buffer.

Attack Vector

The attack is executed over the network against the DNS Server service. An authenticated attacker sends crafted DNS protocol messages that trigger the boundary violation during parsing. The server responds with data that includes leaked bytes from adjacent memory regions.

No verified proof-of-concept code is publicly available. Readers requiring technical specifics should consult the Microsoft Security Update CVE-2026-97841 advisory for authoritative details on the affected code path.

Detection Methods for CVE-2026-97841

Indicators of Compromise

Unusual volumes of malformed or oversized DNS queries directed at internal DNS servers from authenticated hosts.
DNS Server process memory usage anomalies or unexpected crashes correlated with specific client sources.
Outbound DNS responses containing non-standard or binary payloads inconsistent with normal query answers.

Detection Strategies

Enable DNS analytical and debug logging on Windows DNS Servers to capture full query and response contents for forensic review.
Correlate authenticated session telemetry with DNS query patterns to identify low-privilege accounts issuing malformed requests.
Deploy network intrusion detection signatures targeting malformed DNS record types and oversized resource data fields.

Monitoring Recommendations

Baseline normal DNS query distributions and alert on statistical deviations in record types or query sizes.
Monitor Windows Event Logs for DNS Server service restarts, exceptions, or warnings that may indicate exploitation attempts.
Forward DNS telemetry to a centralized analytics platform for longitudinal review and threat hunting.

How to Mitigate CVE-2026-97841

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update CVE-2026-97841 advisory to all affected DNS Servers.
Inventory DNS Server deployments and prioritize patching for internet-facing or multi-tenant environments.
Audit accounts authorized to query internal DNS Servers and remove unnecessary access.

Patch Information

Microsoft has released a security update addressing CVE-2026-97841. Refer to the Microsoft Security Update CVE-2026-97841 advisory for the specific KB articles, affected product versions, and update deployment guidance.

Workarounds

Restrict DNS Server access to trusted network segments using host-based or network firewalls.
Limit DNS query capabilities to authenticated hosts that require them, reducing the authorized attacker pool.
Monitor DNS traffic for malformed queries and apply upstream filtering where feasible until patches can be deployed.

bash

# Configuration example: restrict DNS Server inbound access via Windows Firewall
New-NetFirewallRule -DisplayName "Restrict DNS Server Inbound" `
  -Direction Inbound `
  -Protocol UDP `
  -LocalPort 53 `
  -RemoteAddress 10.0.0.0/8 `
  -Action Allow