CVE-2024-38031: Windows Server 2008 OCSP DoS Vulnerability

CVE-2024-38031 Overview

CVE-2024-38031 is a denial of service vulnerability in the Microsoft Windows Online Certificate Status Protocol (OCSP) Server. The flaw allows an unauthenticated remote attacker to exhaust resources on the OCSP Server component, disrupting certificate revocation checking across the affected environment. The vulnerability is tracked under [CWE-400] Uncontrolled Resource Consumption and affects every supported Windows Server version from 2008 through 2022 23H2. Microsoft published the advisory on July 9, 2024 as part of the monthly Patch Tuesday release. With an EPSS score of 2.538% (82.9 percentile), exploitation interest is meaningful relative to the broader CVE population.

Critical Impact
An unauthenticated network attacker can disrupt OCSP Server availability, breaking certificate revocation validation for clients that rely on the targeted Windows Server.

Affected Products

Microsoft Windows Server 2008 SP2 and Windows Server 2008 R2 SP1
Microsoft Windows Server 2012 and Windows Server 2012 R2
Microsoft Windows Server 2016, 2019, 2022, and 2022 23H2

Discovery Timeline

2024-07-09 - CVE-2024-38031 published to NVD and Microsoft releases security patch
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-38031

Vulnerability Analysis

The vulnerability exists in the Windows OCSP Server role, a component of Active Directory Certificate Services (AD CS) that responds to certificate revocation status queries from clients. An attacker can send crafted OCSP requests across the network to consume server resources without authentication or user interaction. Successful exploitation degrades or halts the OCSP responder, preventing relying parties from validating certificate revocation status. The flaw maps to [CWE-400] Uncontrolled Resource Consumption.

Root Cause

The root cause involves improper limits on resource consumption while the OCSP Server processes inbound revocation queries. Specially formed requests trigger excessive processing or memory use within the OCSP responder service. Microsoft has not published low-level technical details, but the CWE assignment indicates the service does not enforce sufficient throttling or bounds checks on request handling.

Attack Vector

The attack vector is network-based and requires no privileges or user interaction. An attacker reachable to the OCSP responder endpoint, typically over HTTP on TCP/80, can repeatedly submit malformed or resource-intensive OCSP requests. Because OCSP responders are commonly exposed to internal clients and sometimes to the internet, exploitation can disrupt certificate validation workflows across the enterprise PKI.

No public proof-of-concept exploit code is currently available. Microsoft has not reported observed exploitation in the wild, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the Microsoft Security Update CVE-2024-38031 advisory for additional vendor guidance.

Detection Methods for CVE-2024-38031

Indicators of Compromise

Sudden spikes in CPU or memory utilization on servers hosting the OCSP Responder Service (ocspsvc.exe).
HTTP 5xx responses or timeouts from OCSP endpoints under the /ocsp virtual directory in IIS logs.
Abnormally large volumes of inbound OCSP requests from a single source IP or small set of IPs.

Detection Strategies

Monitor Windows Event Logs under Microsoft-Windows-OnlineResponder/Operational for service restarts, request processing errors, and worker process crashes.
Inspect IIS access logs for repeated POST or GET requests to /ocsp with malformed Content-Type headers or oversized payloads.
Correlate network telemetry with PKI health monitoring to identify revocation check failures on downstream clients.

Monitoring Recommendations

Establish performance baselines for ocspsvc.exe and alert on deviations in request latency and throughput.
Track the IIS application pool serving OCSP requests for unexpected recycles or worker process terminations.
Forward OCSP responder and IIS logs to a centralized analytics platform for cross-host correlation and historical analysis.

How to Mitigate CVE-2024-38031

Immediate Actions Required

Apply the July 2024 Microsoft security update referenced in the Microsoft Security Update CVE-2024-38031 advisory to all affected Windows Server systems running the OCSP Responder role.
Identify all hosts with the Online Responder role installed using Get-WindowsFeature ADCS-Online-Cert and prioritize internet-exposed responders.
Restrict inbound access to OCSP endpoints to known PKI clients via firewall rules where business requirements permit.

Patch Information

Microsoft released patches on July 9, 2024 covering Windows Server 2008 SP2, 2008 R2 SP1, 2012, 2012 R2, 2016, 2019, 2022, and 2022 23H2. Administrators should consult the Microsoft Security Update CVE-2024-38031 advisory for the specific KB article and build numbers applicable to each Windows Server version.

Workarounds

Place a rate-limiting reverse proxy or web application firewall in front of the OCSP responder to throttle excessive requests per source IP.
Temporarily disable the Online Responder role on non-essential servers until patches are applied, accepting the operational impact on revocation checking.
Deploy redundant OCSP responders behind a load balancer so that a single resource-exhausted node does not break revocation validation enterprise-wide.

bash

# Inventory Windows Servers with the OCSP Online Responder role installed
Get-WindowsFeature -Name ADCS-Online-Cert | Where-Object { $_.Installed -eq $true }

# Confirm the responder service status after patching
Get-Service -Name OCSPSvc | Format-List Name,Status,StartType