A persistent vulnerability associated to DLL hijacking has been recognized within the Narrator accessibility device, which has been a big concern over time.
This flaw permits malicious actors to take advantage of the device, doubtlessly compromising the safety of programs that depend on it for accessibility options.
Famous initially in studies relationship again to 2013 by professional Hexacorn, the flaw persists in trendy Home windows 10 and 11 variations, permitting attackers with native administrator privileges to realize stealthy code execution, system persistence, and even distant lateral motion.
TrustedSec discovery, impressed by mining techniques from VX-Underground repositories, highlights how on a regular basis accessibility options might be weaponized for malicious ends.
The approach exploits Narrator.exe’s loading of the MSTTSLocOneCoreEnUS.dll from the trail %windirpercentsystem32speech_onecoreenginestts.
By changing this DLL with a malicious model, attackers can execute arbitrary code upon Narrator launch, with out requiring any exports.
The DLL’s DllMain connect operate triggers the payload, however researchers refined it to droop Narrator’s essential thread, silencing the device’s voice output and stopping visible cues that would alert customers.
A proof-of-concept on GitHub demonstrates this evasion, freezing Narrator whereas working customized code undetected.
Person-Degree Persistence through Registry Tweaks
Attackers can embed this hijack to routinely execute at logon by modifying the registry.
Below HKCUSoftwareMicrosoftWindows NTCurrentVersionAccessibility, making a REG_SZ worth named “configuration” set to “Narrator” triggers the DLL on consumer login.
TrustedSec checks confirmed seamless persistence post-logoff, with the malicious DLL loading silently. This technique requires no elevated privileges past preliminary entry, making it excellent for sustaining footholds in consumer contexts.
For broader influence, the approach extends to SYSTEM-level persistence by making use of the identical registry change beneath HKLM, launching Narrator on the login display screen with elevated privileges.
Lateral motion provides one other layer: attackers with distant registry entry through instruments like Impacket can deploy the DLL and alter HKLMSystemCurrentControlSetControlTerminal ServerWinStationsRDP-TcpSecurityLayer to 0.
RDP connection to the goal then permits triggering Narrator through Ctrl+Win+Enter at login, executing the payload as SYSTEM earlier than the session closes, forcing fast course of migration for sustained entry.
Researchers additionally demonstrated “Convey Your Personal Accessibility,” crafting customized accessibility instruments (ATs) through registry exports and imports, pointing to arbitrary executables, even UNC community paths for distant payload supply.
Triggering through ATBroker.exe /begin additional enhances flexibility. Whereas no CVE has been assigned but, this underscores the dangers of unpatched legacy behaviors in accessibility options, urging organizations to observe registry adjustments and DLL paths rigorously.
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