CVE-2025-47979: Windows Failover Cluster Information Disclosure Patch Guide

Microsoft has published an advisory identifying CVE-2025-47979, an information-disclosure vulnerability in Windows Failover Cluster that can cause sensitive data to be written into cluster log files and thereby exposed to a local, low‑privilege attacker; the issue is scored CVSS 3.1 = 5.5 (Medium) and Microsoft lists the vulnerability in its Security Update Guide for administrators to map to the correct patch for their Windows Server builds.

Background / Overview​

Failover clustering is a foundational Windows Server capability for high availability: clusters coordinate multiple nodes to keep services, virtual machines, and storage accessible when individual servers fail. The clustering stack logs operational state, diagnostics, and error information to various traces and persistent log files. In CVE-2025-47979, the root problem is classified as insertion of sensitive information into a log file (CWE-532) — effectively, the cluster writes data into logs that it should not, and those logs are readable by actors with low local privileges. Microsoft’s advisory describes the issue as allowing an authorized local actor to disclose sensitive information from the cluster.
This vulnerability is not a remote code execution flaw; it is an information disclosure bug with a local attack vector. That difference is important operationally: internet exposure is not required, but the high confidentiality impact means the data at risk could be highly sensitive (session tokens, secrets, configuration data, or other operational material) if it is inadvertently logged. Independent aggregator feeds and CVE trackers reflect the same technical summary and the medium CVSS rating.

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Why this matters: security and operational impact​

Failover Cluster components typically run under system or elevated service contexts and coordinate state across nodes. Log outputs from clustering components can therefore contain:

• Administrative configuration and state dumps
• Resource names and connection strings
• Paths and temporary filenames that reference privileged locations
• Diagnostic output that may include snippets of memory or error strings containing tokens

When these outputs are recorded into cluster log files without proper redaction or access constraints, they become a high‑value target for an attacker who can read them. Even a seemingly benign leak — a path, a GUID, or a short token fragment — can materially speed reconnaissance and follow‑on attacks in an enterprise environment. The 2025 patch cycles have repeatedly shown information‑disclosure bugs to be serious because they are often the enabling step for credential theft, lateral movement, or privilege escalation.
Key implications for operations teams:

• This is a local disclosure: network perimeter controls do not prevent a local, low‑privilege user from exploiting the issue if they can read the affected log files.
• The vulnerability raises the importance of least privilege for local accounts on cluster nodes and of strict log‑file access controls.
• Information disclosure is often a stealthy first step in chained attacks — logs can reveal tokens, internal endpoints, or service account names that greatly reduce attacker effort.

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Technical summary and verified facts​

• Nature of the flaw: insertion of sensitive information into log files (CWE‑532). This is not a memory corruption or RCE vector; the flaw occurs when the failover cluster writes data that should have been redacted or guarded.
• Attack vector: Local (Attack Vector = L in the CVSS). An attacker must have some local presence or ability to read cluster log files. The CVSS vector published by vendors indicates low privileges required (PR:L) with no user interaction required.
• Impact: Confidentiality high — sensitive data may be exposed (C). Integrity and availability impacts are reported as none in the published scoring.
• Severity: CVSS v3.1 base score 5.5 (Medium) as reflected in CVE aggregators and vendor feeds.
• Exploitability / Proof-of-concept: As of the advisory and public trackers at publication, there is no public proof-of-concept or observed exploitation in the wild. Aggregators note a patch is available and recommend immediate application.

These elements were cross‑checked with multiple independent aggregators and vulnerability feeds to ensure consistent framing of the risk; the Microsoft Security Update Guide entry remains the vendor authoritative source for exact fixed builds and KB numbers. Note that Microsoft’s Update Guide pages are delivered as a dynamic web application and sometimes require an interactive browser to view the full advisory and precise KB mappings — administrators should use a secure admin workstation to fetch that vendor page and confirm the KBs for their specific Windows Server release(s).

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Attack scenarios and realistic risk models​

• Low-privileged local user reads cluster logs
• Scenario: A contractor, developer, or compromised service account has a low‑privilege shell on a cluster node. The account can access or copy cluster log files (by design or due to lax ACLs) and extract secrets or identifiers that were logged. These artifacts are then used to escalate or pivot.
• Outcome: Information useful for lateral movement (service names, cluster resource identifiers, stored paths, and occasional tokens) is harvested.
• Malicious insider or rogue admin
• Scenario: An internal actor with legitimate but limited access purposefully searches logs for mislogged secrets.
• Outcome: Direct exfiltration of sensitive configuration or credential information.
• Chaining with other vulnerabilities
• Scenario: An attacker uses leaked tokens or endpoints discovered in cluster logs to target other services (Remote Desktop, admin portals, or management APIs).
• Outcome: A local information leak becomes a stepping stone to privilege escalation or wider access in the estate.

Because the attack vector is local, organisations with shared admin workstations, weak separation between admin and user networks, or permissive local ACLs on logs are at higher risk. For cloud‑hosted nodes and managed service providers, multi‑tenant exposures can be aggravated if log access is not strictly segmented.

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What Microsoft says and how to verify the patch​

Microsoft lists CVE‑2025‑47979 in the Security Update Guide and provides remedial updates targeted at the affected Windows Server builds. Administrators must follow the MSRC advisory to map the CVE to the exact KB (cumulative update or security-only rollup) that applies to their Server branch. Because the Update Guide is dynamic, the recommended process is:

• Use a secured admin workstation and open the Microsoft Security Update Guide entry for CVE-2025-47979.
• Record the KB article number(s) Microsoft lists for your Windows Server SKU (Server 2025, Server 2022 23H2, or other listed builds).
• Download the appropriate cumulative update or use Windows Update / WSUS / Intune / SCCM to stage the patch in your management channel.
• Validate the host reflects the installed KB via Get-HotFix or the Windows Update history UI.

Multiple independent feeds note that a patch is available and that organizations should install it; these trackers also report the CVSS score and the local attack vector. Administrators should treat MSRC as the source of record and cross‑check third‑party listings if there is any mismatch in CVE → KB mappings.
Cautionary note: third‑party CVE aggregators occasionally list affected product versions before vendor KBs are fully mapped to particular builds. Always use Microsoft’s Security Update Guide or the Microsoft Update Catalog to confirm the exact KB package for your environment. The MSRC page itself may require interactive rendering, so ensure you fetch it from an administrative machine that is appropriately hardened.

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Detection, mitigation, and immediate actions​

Short‑term (0–24 hours)

• Inventory cluster nodes and determine who has local accounts on them. Use your asset management tooling or PowerShell to enumerate cluster roles and nodes.
• Restrict local account access: remove shared or unnecessary local accounts; move interactive activity to jump hosts with tighter controls.
• Lock down log file permissions: ensure cluster log directories are accessible only to administrators. Enforce ACLs to prevent low‑privilege reads where possible.
• Monitor for suspicious access to cluster logs: ingest file‑access events into your SIEM and watch for non‑admin reads of cluster log paths.

Medium‑term (24–72 hours)

• Patch cluster nodes according to Microsoft’s KB mapping in the MSRC Update Guide.
• Rotate any credentials or secrets that you can confirm were present or at risk in logs. If rotation is impractical for some secrets, assume compromise and plan for containment.
• Harden audit and monitoring for cluster administrative actions (service startups, scheduled tasks, unexpected process creation).

Longer‑term

• Apply least privilege design to cluster operations. Use dedicated service accounts with scoped permissions and restrict who can log onto nodes.
• Redact or avoid logging of secrets: review cluster diagnostic levels and the content of logging routines to avoid recording sensitive material.
• Segregate administrative and operational networks and ensure jump boxes for admin access are tightly controlled.

Example practical checks (PowerShell)

• List cluster nodes and roles to confirm which servers need immediate attention.
• Get-Cluster | Select Name, NodeWeight, ClusterFunctionalLevel
• Verify log directories and ACLs:
• Get-Acl -Path 'C:\Windows\Cluster\Reports' | Format-List

If you cannot patch immediately, reducing the set of accounts that can read cluster logs and isolating cluster nodes on admin‑only networks materially lowers risk.

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Detection and hunting guidance​

• Look for unusual file reads on cluster log paths (e.g., C:\Windows\Cluster* and configured log destinations). Correlate file read events with user context and time of day.
• Map access to known low‑privilege accounts and non‑administrator sessions. Use endpoint telemetry to detect file access by unexpected processes.
• Correlate with lateral movement patterns: after local log access, look for attempts to call cluster management APIs, remote administration tools, or credential dumping activity.
• Implement alerting on reads by non‑admin principals to cluster logs and require analyst review.

Example Kusto-style query (generic / adjust to product):

• DeviceFileEvents
  | where FileName has "Cluster" or FolderPath has "Windows\Cluster"
  | where InitiatingProcessAccountName != "SYSTEM" and InitiatingProcessAccountName != "Administrator"

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Strengths of Microsoft’s response and observed gaps​

Strengths

• Microsoft has recorded and published the advisory, assigned a CVE, and released fixes to address the logging issue — this provides a clear path to remediation for varying Windows Server builds. Third‑party vulnerability feeds and aggregators consistently report the CVSS score and the local attack vector, corroborating the vendor’s technical summary.
• The classification as CWE‑532 (sensitive information in logs) is an actionable category: defenders can focus on ACL hardening and log content reviews immediately.

Risks and gaps

• The attack vector is local, so environments that allow broad local access (shared admin credentials, developer access, or lax workstation segregation) remain exposed even after perimeter hardening.
• Vendor Update Guide pages are dynamic and sometimes hard to scrape; organizations using automated tools to map CVEs to KBs should confirm MSRC entries in an interactive browser to avoid mis‑patching. Community advisories in mid‑2025 show mismatches between CVE identifiers and KB numbers across feeds — this is a recurring operational hazard.
• Even after a patch is applied, residual data may remain in existing log files. Administrators must consider log retention policies: patched systems may still have exposures in archived logs unless those logs are sanitized or rotated and protected. Aggregators specifically warn that applying the fix does not retroactively remove sensitive entries already written to disk.

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Practical checklist for administrators (step-by-step)​

• Confirm vulnerability applicability:
• Use Microsoft’s Security Update Guide entry for CVE‑2025‑47979 to determine affected versions and KB numbers. Fetch the page on a secure admin workstation and capture the KBs for your build(s).
• Inventory and prioritize:
• Identify cluster nodes, their roles, and which are internet‑facing or accessible to a broad set of users. Prioritize production clusters and nodes hosting critical VMs.
• Limit local access:
• Immediately remove non‑essential local accounts from cluster nodes and enforce unique admin accounts.
• Patch:
• Apply the KB(s) Microsoft lists for your exact Windows Server build using your patch management toolchain. Stage patches through test → pilot → production rings.
• Sanitize logs:
• Rotate or remove archived logs that may contain sensitive entries; consider secure deletion if those logs are confirmed to contain secrets.
• Rotate secrets where practical:
• Any credentials that might have been exposed should be rotated — service accounts, certificates, or connection strings that are feasible to rotate quickly.
• Monitor and alert:
• Create SIEM alerts for non‑admin reads of log directories and any anomalous cluster administrative actions.
• Document and communicate:
• Update incident response and runbook content to reflect the new vector; inform stakeholders of actions taken and risk posture changes.

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Cross‑verification and caveats​

This analysis cross‑checked vendor and multiple independent vulnerability trackers to validate the technical summary, CVSS score, and attack vector:

• Independent CVE trackers and vulnerability aggregators list CVE‑2025‑47979 with a CVSS v3.1 base score of 5.5 and a local attack vector, consistent with Microsoft’s advisory summary.
• Threat‑intelligence and feed services reiterate the confidentiality impact and patch availability, and emphasize that applying the patch does not sanitize past logs — operators should rotate or remove historical logs if sensitive content is a concern.
• Community and forum archives show a recurring pattern where cluster and RRAS‑class vulnerabilities in 2025 were prioritized in Microsoft patch cycles; historical advisory handling underscores the importance of mapping CVEs to KBs using the MSRC Update Guide. This pattern suggests administrators should pay special attention to Update Guide mappings and not rely blindly on secondary aggregators.

Unverifiable or ambiguous claims

• Public feeds sometimes differ on the exact affected SKU list or the KB mapping until Microsoft’s Update Guide is fully populated and referenced in the Microsoft Update Catalog. If any external scanner or ticket references a CVE→KB mapping that differs from Microsoft’s page, treat that as unverified until you confirm it with MSRC and the Microsoft Update Catalog in an interactive browser.

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Risk rating and prioritization guidance​

• Immediate priority: Systems where multiple users have local access to cluster nodes, production clusters hosting critical workloads, and nodes with broad retained log archives. These environments should be patched and logs sanitized promptly.
• Medium priority: Clusters in locked‑down administrative domains with tightly controlled local accounts, but which nevertheless retain long log retention windows.
• Lower priority: Lab or disposable clusters used for testing, though best practice remains to patch these too to avoid developer‑stage credential leakage.

Even though the CVSS base score is “Medium” (5.5), the practical business impact can be high when the disclosed logs include service account credentials, API tokens, or other secrets. Thus, prioritize remediation where sensitive workloads or PII might be exposed.

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Final analysis and recommendations​

CVE‑2025‑47979 is a concrete example of why logging design and log‑file access control matter as much as code hardening. The vulnerability’s mechanics are straightforward — the cluster wrote sensitive data into logs — but the operational consequences are amplified by the privileged context of cluster components and the potential for logs to leak secrets that enable follow‑on compromises.
Recommended immediate actions:

• Confirm the MSRC advisory and the exact KB(s) to install for each Windows Server build you run.
• Patch cluster nodes in a prioritized manner (production high, then staging, then dev).
• Harden local account usage and log file ACLs; rotate any credentials that could plausibly have been recorded in logs.
• Sanitize or rotate historical logs that may contain sensitive data retained prior to the patch.
• Implement monitoring to flag non‑admin reads of cluster log paths and anomalous cluster management activity.

This issue underscores a broader operational truth: logging and telemetry are double‑edged. They are essential for troubleshooting and operations, but if logs are not curated, redacted, and access‑controlled, they become a persistent source of secrets leakage. Patching closes the immediate code defect, but full remediation requires access governance, log hygiene, and monitoring improvements to prevent similar exposures in future.
Administrators should consult Microsoft’s Security Update Guide entry for CVE‑2025‑47979 to obtain the authoritative KB numbers and deploy the appropriate updates in their environment as the first step.

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Conclusion
CVE‑2025‑47979 is a medium‑scored but operationally meaningful Failover Cluster information‑disclosure vulnerability that demonstrates how logging mistakes in privileged subsystems can become high‑value reconnaissance for attackers. The vendor has published fixes; organizations must patch promptly, secure log access, and treat residual historical log content as a real remediation task. Prioritize hardening of local account access and log retention policies alongside the technical patch to fully address the threat.

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Source: MSRC Security Update Guide - Microsoft Security Response Center