Microsoft Patches Critical Windows Remote Assistance Vulnerability (CVE-2026-20824)
On January 13, 2026, Microsoft released security updates addressing CVE-2026-20824, a security feature bypass vulnerability in Windows Remote Assistance that allows attackers to evade Mark of the Web (MOTW) protections. The flaw affects a broad range of Windows versions, including Windows 10 (21H2/22H2), Windows 11 (23H2/24H2/25H2), and Windows Server (2012–2025), with patches delivered via cumulative updates (e.g., KB5073724, KB5073455, KB5073457).
Technical Details & Exploitation
The vulnerability stems from how Windows Remote Assistance processes specially crafted files, enabling attackers to bypass security checks designed to flag untrusted content. While the flaw does not grant remote code execution (RCE), it can be exploited to:
- Evade MOTW-driven defenses, such as SmartScreen and Office macro restrictions.
- Weaken downstream security tools that rely on MOTW flags to determine file trust levels.
- Enable stealthy data exfiltration by making malicious files appear as locally trusted content.
Exploitation requires user interaction victims must open a malicious file delivered via email, instant messaging, or a compromised website. Attackers may leverage social engineering to trick users into executing the payload.
Impact & Severity
- CVSS v3.1 Base Score: 5.5 (Temporal: 4.8) – Rated "Important" by Microsoft.
- Attack Vector: Local (AV:L), requiring no privileges (PR:N) and low complexity (AC:L).
- Impact: High confidentiality risk (C:H), with no direct effect on integrity or availability (I:N/A:N).
- Exploitability: Currently assessed as "Exploitation Less Likely", with no known in-the-wild attacks at the time of disclosure.
Mitigation & Response
Microsoft urges administrators to deploy the January 2026 Patch Tuesday updates to restore proper MOTW enforcement. Until patches are applied, organizations are advised to:
- Tighten email and web filtering to block malicious attachments.
- Restrict Windows Remote Assistance in high-risk environments.
- Reinforce user awareness regarding unsolicited assistance requests and unknown file downloads.
The vulnerability highlights a growing trend of MOTW bypass techniques, where attackers exploit flaws not for direct RCE but to undermine foundational security controls.
Source: https://gbhackers.com/motw-bypassing-remote-assistance/
Microsoft Security Response Center cybersecurity rating report: https://www.rankiteo.com/company/microsoft-security-response-center
"id": "MIC1769045546",
"linkid": "microsoft-security-response-center",
"type": "Vulnerability",
"date": "6/2012",
"severity": "25",
"impact": "1",
"explanation": "Attack without any consequences"{'affected_entities': [{'industry': 'Software',
'location': 'Global',
'name': 'Microsoft',
'type': 'Technology Company'}],
'attack_vector': 'Local',
'data_breach': {'data_exfiltration': 'Possible stealthy data exfiltration'},
'date_publicly_disclosed': '2026-01-13',
'description': 'On January 13, 2026, Microsoft released security updates '
'addressing CVE-2026-20824, a security feature bypass '
'vulnerability in Windows Remote Assistance that allows '
'attackers to evade Mark of the Web (MOTW) protections. The '
'flaw affects a broad range of Windows versions, enabling '
'attackers to bypass security checks designed to flag '
'untrusted content, weaken downstream security tools, and '
'enable stealthy data exfiltration.',
'impact': {'systems_affected': 'Windows 10 (21H2/22H2), Windows 11 '
'(23H2/24H2/25H2), Windows Server (2012–2025)'},
'lessons_learned': 'The vulnerability highlights a growing trend of MOTW '
'bypass techniques, where attackers exploit flaws not for '
'direct RCE but to undermine foundational security '
'controls.',
'post_incident_analysis': {'corrective_actions': 'Apply security patches and '
'reinforce security controls',
'root_causes': 'Flaw in how Windows Remote '
'Assistance processes specially '
'crafted files, enabling bypass of '
'MOTW protections'},
'recommendations': ['Deploy the January 2026 Patch Tuesday updates',
'Tighten email and web filtering to block malicious '
'attachments',
'Restrict Windows Remote Assistance in high-risk '
'environments',
'Reinforce user awareness regarding unsolicited '
'assistance requests and unknown file downloads'],
'references': [{'source': 'Microsoft Security Update Guide'}],
'response': {'containment_measures': ['Deploy January 2026 Patch Tuesday '
'updates (e.g., KB5073724, KB5073455, '
'KB5073457)',
'Tighten email and web filtering to '
'block malicious attachments',
'Restrict Windows Remote Assistance in '
'high-risk environments',
'Reinforce user awareness regarding '
'unsolicited assistance requests and '
'unknown file downloads'],
'remediation_measures': 'Apply security patches (KB5073724, '
'KB5073455, KB5073457)'},
'title': 'Microsoft Patches Critical Windows Remote Assistance Vulnerability '
'(CVE-2026-20824)',
'type': 'Security Feature Bypass',
'vulnerability_exploited': 'CVE-2026-20824'}