CVE-2026-77827: Maono Link Privilege Escalation Flaw

CVE-2026-77827 Overview

CVE-2026-77827 is a local privilege escalation vulnerability in the MaonoAiServices Windows service shipped with Maono Link 3.8.13. The service grants improper write privileges to the C:\ProgramData\Maono directory, allowing a standard user account to escalate privileges on the host. The issue is classified under [CWE-428] Unquoted or otherwise mutable service resource paths and directory permissions. Maono resolved the flaw in version 4.0.80. Local attack vectors of this class are frequently chained with initial-access techniques to reach SYSTEM on affected Windows endpoints.

Critical Impact
A low-privileged local user can replace or plant files within a service-controlled directory to execute code with the privileges of the MaonoAiServices Windows service.

Affected Products

Maono Link 3.8.13 (MaonoAiServices Windows service)
Maono Link versions prior to 4.0.80
Windows endpoints with the Maono Link software installed

Discovery Timeline

2026-09-08 - CVE-2026-77827 published to NVD
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-77827

Vulnerability Analysis

The MaonoAiServices Windows service loads and executes resources from C:\ProgramData\Maono under a privileged security context. Because the directory is created with permissions that allow standard (non-administrative) users to write to it, any local user can drop or replace files that the service later loads. When the service consumes the attacker-controlled content, code executes with the elevated privileges assigned to the service account.

This pattern falls under [CWE-428], where a privileged process trusts a mutable filesystem location. The result is a reliable local privilege escalation path from an interactive user session to the service context, typically SYSTEM on Windows.

Root Cause

The root cause is an insecure Access Control List (ACL) on the C:\ProgramData\Maono directory tree created by the Maono Link installer. Standard users inherit write access to a directory that a higher-privileged Windows service reads from at runtime. The service does not validate the integrity or origin of the files it loads from this path.

Attack Vector

Exploitation requires local access with a standard user account. No user interaction is required beyond the attacker's own actions. An attacker with a session on the endpoint writes a malicious payload (for example, a substituted binary, DLL, or configuration file) into C:\ProgramData\Maono. When MaonoAiServices next reads or executes that resource, the attacker's code runs at the service's privilege level, granting full control of the host.

No public proof-of-concept, exploit code, or CISA KEV listing is currently associated with this CVE. Refer to the CISA CSAF Document and the CVE-2026-77827 Record for authoritative technical detail.

Detection Methods for CVE-2026-77827

Indicators of Compromise

Unexpected file creation, modification, or replacement events within C:\ProgramData\Maono originating from non-administrative users.
New executable, DLL, or script files appearing in the Maono directory that were not written by the Maono installer or updater.
Child processes spawned by MaonoAiServices that do not match the vendor's expected process tree.

Detection Strategies

Enable Windows object access auditing on C:\ProgramData\Maono and alert on write events from non-SYSTEM, non-Administrator accounts.
Monitor Windows Service Control Manager events for MaonoAiServices restarts that immediately follow file writes in the ProgramData directory.
Hunt for process lineage where MaonoAiServices spawns command interpreters (cmd.exe, powershell.exe) or other unexpected LOLBins.

Monitoring Recommendations

Ingest Sysmon Event ID 11 (FileCreate) and Event ID 1 (ProcessCreate) telemetry for the Maono directory and service into your SIEM.
Baseline the legitimate contents and hashes of C:\ProgramData\Maono after patching and alert on drift.
Correlate local logon events with subsequent file writes in service-owned ProgramData directories to surface privilege escalation attempts.

How to Mitigate CVE-2026-77827

Immediate Actions Required

Upgrade Maono Link to version 4.0.80 or later on all Windows endpoints running the software.
Inventory endpoints with Maono Link installed and prioritize systems used by low-privileged or shared user accounts.
Restrict the ACL on C:\ProgramData\Maono to remove write access for the Users group until patching is complete.

Patch Information

The vendor addressed CVE-2026-77827 in Maono Link 4.0.80. Refer to the Maono Link Software Overview for the current release and to the CISA CSAF Document for the vendor-coordinated advisory content.

Workarounds

Manually harden the C:\ProgramData\Maono directory ACL to allow write access only to SYSTEM and Administrators.
Stop and disable the MaonoAiServices Windows service on endpoints where the Maono Link software is not required.
Enforce standard-user least privilege and application allowlisting to limit which binaries can execute from ProgramData paths.

bash

# Configuration example: remove write access for standard users on the affected directory
icacls "C:\ProgramData\Maono" /remove:g "BUILTIN\Users"
icacls "C:\ProgramData\Maono" /inheritance:r
icacls "C:\ProgramData\Maono" /grant:r "NT AUTHORITY\SYSTEM:(OI)(CI)F" "BUILTIN\Administrators:(OI)(CI)F" "BUILTIN\Users:(OI)(CI)RX"