CVE-2026-69790: Windows Credential Providers Privilege Escalation

CVE-2026-69790 Overview

CVE-2026-69790 is a heap-based buffer overflow [CWE-122] in Windows Credential Providers. An authenticated local attacker can trigger the overflow to elevate privileges on an affected Windows system. Microsoft classifies the issue as an elevation of privilege vulnerability with high impact to confidentiality, integrity, and availability.

The flaw resides in the Credential Providers component, which handles authentication workflows through the Local Security Authority. Successful exploitation grants the attacker higher-privileged code execution on the target host. Microsoft has published guidance in the Microsoft Security Update Guide.

Critical Impact
A local authenticated attacker can corrupt heap memory in Windows Credential Providers to gain elevated privileges, breaking the boundary between standard user and administrative contexts.

Affected Products

Microsoft Windows (Credential Providers component)
Specific Windows versions and build numbers are enumerated in the Microsoft Security Update Guide
Refer to Microsoft's advisory for the authoritative list of impacted SKUs and KB article identifiers

Discovery Timeline

2026-09-08 - CVE-2026-69790 published to the National Vulnerability Database
2026-09-09 - Last updated in the NVD database

Technical Details for CVE-2026-69790

Vulnerability Analysis

The vulnerability is a heap-based buffer overflow [CWE-122] in Windows Credential Providers. Credential Providers are COM objects loaded by LogonUI.exe and consumed by the Local Security Authority to gather and validate user credentials during interactive logon, unlock, and credential change flows.

An authorized attacker with local access can supply crafted input to a vulnerable Credential Provider code path. The component allocates a heap buffer whose size does not correctly bound the copied data, allowing adjacent heap memory to be corrupted. Because Credential Providers execute in a higher-privileged authentication context, memory corruption in this path enables privilege elevation rather than only user-level impact.

The attack does not require user interaction and can be executed by any account with local logon rights. Successful exploitation compromises confidentiality, integrity, and availability of the host. EPSS currently estimates a low near-term exploitation probability, but the local privilege escalation profile is attractive as a post-compromise primitive.

Root Cause

The root cause is improper validation of a length or size value used to allocate or write into a heap buffer inside a Credential Provider routine. When attacker-controlled data exceeds the allocated region, the write overruns adjacent heap chunks, enabling manipulation of heap metadata or object pointers used by the authentication pipeline.

Attack Vector

Exploitation requires local access with low privileges and no user interaction. An attacker triggers the vulnerable code path through a Credential Provider interface, such as during logon UI interactions or a programmatic call that reaches the component. Corruption of heap-resident objects can then be leveraged to redirect execution or manipulate authentication state, yielding SYSTEM-level privileges.

No public proof-of-concept exploit has been observed, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. See the Microsoft Security Update Guide for vendor-provided technical detail.

Detection Methods for CVE-2026-69790

Indicators of Compromise

Unexpected crashes or Windows Error Reporting entries referencing LogonUI.exe, lsass.exe, or Credential Provider DLLs
New or unsigned DLLs registered under HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\Credential Providers
Unexpected child processes spawned by LogonUI.exe or authentication-related services
Local account privilege changes shortly after interactive logon events

Detection Strategies

Enable Windows Error Reporting collection and alert on repeated faults in authentication binaries, which can indicate exploitation attempts against the heap allocator
Monitor Sysmon Event ID 7 (ImageLoad) for unexpected modules loaded into LogonUI.exe or by processes registering Credential Providers
Correlate Security Event ID 4672 (special privileges assigned) with prior 4624 logons from low-privilege accounts to surface anomalous elevation
Baseline the set of registered Credential Providers and alert on additions or modifications to the corresponding registry keys

Monitoring Recommendations

Ingest endpoint process, image load, and registry telemetry into a centralized analytics platform for retrospective hunting
Track patch compliance for the Microsoft security update addressing CVE-2026-69790 across all Windows endpoints and servers
Review authentication logs for unusual sequences of failed logons followed by privilege escalation events

How to Mitigate CVE-2026-69790

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update Guide to all affected Windows systems
Prioritize patching on multi-user hosts, jump servers, and workstations used by privileged administrators
Audit local account membership and remove unnecessary interactive logon rights
Verify that endpoint protection is active and reporting on all Windows endpoints

Patch Information

Microsoft has published a security update for CVE-2026-69790 through the standard Windows Update and Microsoft Update Catalog channels. Consult the Microsoft Security Update Guide for the specific KB identifiers, build numbers, and offline update packages that correspond to each supported Windows release.

Workarounds

No official vendor workaround is documented; applying the security update is the supported remediation
Restrict interactive and Remote Desktop logon rights to reduce the population of accounts that could reach the vulnerable code path
Enforce least privilege and disable unused third-party Credential Providers that are not required for business operations
Enable Credential Guard and LSA protection where supported to harden the authentication attack surface

bash

# Verify installation of the Windows security update on an endpoint
# Replace KBXXXXXXX with the KB identifier listed in the MSRC advisory for your Windows build
wmic qfe list brief | findstr /I "KBXXXXXXX"

# Enumerate registered Credential Providers for review
reg query "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\Credential Providers" /s