CVE-2025-47978 Overview
CVE-2025-47978 is an out-of-bounds read vulnerability in the Windows Kerberos authentication component. An authorized attacker can exploit the flaw over a network to trigger a denial-of-service condition on affected Windows Server systems. The issue is tracked under CWE-125: Out-of-bounds Read and impacts Windows Server 2022, Windows Server 2022 23H2, and Windows Server 2025. Microsoft addressed the vulnerability in its July 2025 security update cycle. No public proof-of-concept exploit is available, and the flaw is not listed in the CISA Known Exploited Vulnerabilities catalog.
Critical Impact
Successful exploitation disrupts Kerberos authentication services, preventing legitimate users from authenticating to domain resources across affected Windows Server deployments.
Affected Products
- Microsoft Windows Server 2022
- Microsoft Windows Server 2022 23H2
- Microsoft Windows Server 2025
Discovery Timeline
- 2025-07-08 - CVE-2025-47978 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-47978
Vulnerability Analysis
The vulnerability resides in the Windows Kerberos implementation, which handles authentication for Active Directory and networked services. Kerberos processes ticket and authentication messages containing structured fields with declared and actual length values. When the component reads beyond an allocated buffer boundary while parsing these fields, it accesses memory that was not intended for that operation. The out-of-bounds read causes the Kerberos service to terminate abnormally, resulting in denial of service. Availability of authentication on the affected server is impacted, while confidentiality and integrity of data remain unaffected. The EPSS score of 2.044% reflects a moderate probability of exploitation activity relative to the broader CVE population.
Root Cause
The root cause is improper validation of length or offset values during Kerberos message parsing. The parser reads beyond the end of a buffer because size checks against attacker-influenced fields are insufficient. This is classified as CWE-125: Out-of-bounds Read.
Attack Vector
Exploitation requires network access and valid domain credentials. An authenticated attacker sends a specially crafted Kerberos message to the target server. The malformed input drives the parser past buffer boundaries, crashing the service. Because domain controllers depend on Kerberos, disruption cascades to Kerberos-authenticated workloads across the environment. No user interaction is required. See the Microsoft CVE-2025-47978 Advisory for vendor-specific details on the affected code path.
Detection Methods for CVE-2025-47978
Indicators of Compromise
- Unexpected termination or restart of the Kerberos Key Distribution Center (KDC) service on domain controllers.
- Windows Event Log entries indicating Kerberos service crashes, application errors, or Local Security Authority Subsystem Service (LSASS) faults.
- Spikes in failed authentication events across the domain coinciding with malformed Kerberos traffic.
Detection Strategies
- Monitor for anomalous Kerberos protocol messages arriving at TCP/UDP port 88, particularly from authenticated but unusual source hosts.
- Correlate KDC service failures with preceding inbound Kerberos requests to identify potential exploitation attempts.
- Deploy network detection rules that flag Kerberos AS-REQ or TGS-REQ messages with malformed ASN.1 encoding or oversized fields.
Monitoring Recommendations
- Enable Windows Security and System event log forwarding from all domain controllers to a centralized logging platform.
- Baseline normal Kerberos request volumes per host and alert on statistical deviations.
- Track service restart counts for Kerberos, KDC, and LSASS processes on Windows Server 2022, 2022 23H2, and 2025.
How to Mitigate CVE-2025-47978
Immediate Actions Required
- Apply the July 2025 Microsoft security update addressing CVE-2025-47978 to all affected Windows Server systems.
- Prioritize patching of domain controllers, since Kerberos disruption on these systems affects authentication across the environment.
- Audit domain accounts and reduce standing privileges to limit the population of users capable of exploiting the flaw.
Patch Information
Microsoft published fixes for Windows Server 2022, Windows Server 2022 23H2, and Windows Server 2025 through the standard Windows Update channel. Refer to the Microsoft CVE-2025-47978 Advisory for the specific KB article and build numbers applicable to each release.
Workarounds
- No official vendor workaround exists; patching is the recommended remediation.
- Restrict inbound access to Kerberos ports (TCP/UDP 88) so that only trusted network segments can reach domain controllers.
- Enforce network segmentation and require jump hosts for administrative traffic to reduce the exposure surface to authenticated attackers.
- Deploy redundant domain controllers so that a single Kerberos service crash does not halt authentication for the entire domain.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
