Microsoft has published details of CVE-2026-20824 as a security feature bypass vulnerability in Windows Remote Assistance, assigning it an “Important” severity rating with a CVSS v3.1 base score of 5.5 (temporal 4.8).
The issue is categorized under CWE-693 (Protection Mechanism Failure), meaning core defensive checks do not work as intended under specific conditions.
The flaw is local in nature (AV:L) but requires no privileges (PR:N) and only low attack complexity (AC:L), making it attractive in post-compromise or insider scenarios.
Successful exploitation leads to high impact on confidentiality (C:H) while leaving integrity and availability unaffected (I:N/A:N), aligning with a data-exfiltration or stealth-evasion risk rather than full system takeover.
Microsoft currently rates exploitability as “Exploitation Less Likely,” with no public exploits or in-the-wild attacks reported at the time of release.
Technically, the vulnerability stems from how Windows Remote Assistance processes specially crafted files involved in initiating or handling assistance sessions, allowing an attacker to bypass security checks that normally apply to untrusted content.
By exploiting this protection failure, an attacker can evade MOTW-driven safeguards such as certain SmartScreen and Office or scripting restrictions that are normally enforced when files originate from the internet zone.
This places CVE-2026-20824 in a growing class of Windows MOTW bypasses where the core danger is not a new code execution vector, but the ability to run or open content under a more trusted context than it should have.
Attack Scenarios, Affected Versions, and Patching
Exploitation requires user interaction (UI:R), as victims must open a specially crafted file delivered via email, instant message, or a web download to trigger the Remote Assistance logic.
In an email scenario, an attacker sends the malicious file and relies on social engineering to convince the user to open it; in a web scenario, the attacker hosts the file on a controlled or compromised site and lures the user into clicking and then opening it locally.
Because the vulnerability is local and does not directly provide remote code execution, it is most powerful when chained with other bugs or used by threat actors who already have limited access and want to quietly bypass content-origin protections.
Microsoft confirms that a successful exploit allows evasion of Mark of the Web defenses, undermining downstream security tools and workflows that depend on MOTW flags to decide how aggressively to scan or sandbox content.
This could, for example, reduce warning prompts, weaken macro or script restrictions, or help malicious payloads appear as trusted local files even though they came from an external source.
CVE-2026-20824 affects a wide range of supported Windows client and server releases, including Windows 10 21H2 and 22H2, Windows 11 23H2, 24H2, and 25H2, along with Windows Server 2012, 2012 R2, 2016, 2019, 2022, and the new Windows Server 2025, with fixes delivered in the January 13, 2026 Patch Tuesday updates.
The patches ship in cumulative or monthly rollup updates such as KB5073724 (Windows 10 21H2/22H2), KB5073455 (Windows 11 23H2), KB5074109 (Windows 11 24H2/25H2), KB5073457 (Windows Server 2022), KB5073379 (Windows Server 2025), KB5073723 (Windows 10 1809/Windows Server 2019), and related KBs for older server editions.
Microsoft labels customer action as required, urging administrators to deploy the January 13, 2026 security updates across all affected Windows builds to restore proper MOTW enforcement for Remote Assistance.
Until updates are fully rolled out, organizations should tighten email and web filtering, restrict use of Windows Remote Assistance in high-risk environments, and reinforce user awareness around unsolicited assistance invitations and unknown file attachments.
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