CVE-2026-62810: AD CS Privilege Escalation Vulnerability

CVE-2026-62810 Overview

CVE-2026-62810 is a heap-based buffer overflow vulnerability in Microsoft Active Directory Certificate Services (AD CS). An authorized local attacker can exploit the flaw to elevate privileges on an affected system. The weakness is classified as [CWE-122], heap-based buffer overflow, and requires low privileges without user interaction. Successful exploitation results in high impact to confidentiality, integrity, and availability of the target host. Microsoft published the advisory through the Microsoft Security Response Center on September 8, 2026.

Critical Impact
A local authenticated attacker can corrupt heap memory in AD CS to gain elevated privileges, potentially compromising certificate issuance and the trust chain of the enterprise PKI.

Affected Products

Microsoft Windows Server running Active Directory Certificate Services (AD CS)
Enterprise Certificate Authority roles hosted on affected Windows Server versions
Refer to the Microsoft Security Update Guide CVE-2026-62810 for the authoritative list of affected builds

Discovery Timeline

2026-09-08 - CVE-2026-62810 published to NVD
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-62810

Vulnerability Analysis

The vulnerability resides in Active Directory Certificate Services, the Windows Server role that issues and manages digital certificates for an enterprise PKI. AD CS mishandles memory allocation during processing of attacker-controlled input, allowing data to be written past the bounds of an allocated heap buffer. An authorized attacker with local access can trigger the overflow to corrupt adjacent heap structures. Successful exploitation leads to arbitrary code execution in the context of the AD CS service, which typically runs with elevated privileges on the certificate authority host.

Because AD CS underpins certificate issuance, code execution in this service can be leveraged to influence certificate templates, issue rogue certificates, or pivot to broader Active Directory compromise. The attack vector is local and complexity is low, but the attacker must already hold a valid account on the target system.

Root Cause

The root cause is a heap-based buffer overflow [CWE-122] in AD CS input processing. The service allocates a heap buffer without sufficiently validating the size of incoming data, allowing an oversized write that corrupts heap metadata or adjacent objects. Microsoft has not published low-level technical details of the vulnerable component.

Attack Vector

Exploitation requires local access and a valid low-privileged account on the host running AD CS. The attacker submits crafted input that reaches the vulnerable code path within the service and triggers the overflow. No user interaction is required, and the scope is unchanged. See the Microsoft Security Update Guide CVE-2026-62810 for vendor guidance. Public proof-of-concept code is not available at the time of publication, and the EPSS probability remains low.

No verified exploit code is available. Refer to the vendor advisory for technical specifics as Microsoft releases additional detail.

Detection Methods for CVE-2026-62810

Indicators of Compromise

Unexpected crashes or restarts of the certsvc service on certificate authority hosts
Windows Error Reporting entries referencing AD CS binaries with heap corruption signatures
Anomalous certificate issuance events, especially for high-privilege templates or accounts
New or modified certificate templates outside of change-management windows

Detection Strategies

Correlate AD CS service crashes with process creation events from low-privileged local accounts on the CA host
Monitor Windows Event Log source Microsoft-Windows-CertificationAuthority for abnormal request patterns and failures
Baseline normal certificate request volume and alert on spikes originating from a single local account
Hunt for local privilege escalation behaviors on CA servers, including token manipulation and unexpected child processes of certsrv.exe

Monitoring Recommendations

Enable enhanced auditing on AD CS servers, including object access and privilege use audit categories
Forward AD CS event logs to a central analytics platform for correlation across the identity plane
Track binary integrity of AD CS components and alert on unsigned or modified DLLs loaded by certsrv.exe
Review issued certificate logs daily for entries mapping to sensitive accounts or unusual EKUs

How to Mitigate CVE-2026-62810

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update Guide CVE-2026-62810 to all Windows Servers running the AD CS role
Inventory every certificate authority in the environment, including subordinate and offline CAs, and prioritize patching enterprise issuing CAs
Restrict local logon rights on CA hosts to a minimal set of tier-0 administrators
Review recently issued certificates and revoke any that appear anomalous

Patch Information

Microsoft addressed CVE-2026-62810 in the security update published on September 8, 2026. Consult the Microsoft Security Update Guide CVE-2026-62810 for the specific KB articles and build numbers that apply to each Windows Server version.

Workarounds

No official workaround has been published by Microsoft; patching is the required remediation
Reduce exposure by removing interactive and remote logon rights for non-administrative users on CA hosts
Segment CA servers on isolated management networks and enforce jump-host access
Monitor and constrain certificate template permissions to prevent abuse if the service is compromised

bash

# Verify installed updates on a Windows Server running AD CS
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20

# Confirm the AD CS service state and restart after patching
Get-Service certsvc
Restart-Service certsvc