EUVD-2026-56712
GHSA-5x9p-4gjr-5pr3
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Local file-open trigger requires active user interaction but zero attacker OS privilege; full user-session compromise with unchanged scope aligns with document-parser exploitation pattern.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Untrusted pointer dereference in Microsoft Office allows an unauthorized attacker to execute code locally.
AnalysisAI
Local code execution via untrusted pointer dereference in Microsoft Office affects multiple product lines - Microsoft 365 Apps for Enterprise, Office 2019, Office LTSC 2021/2024, and Mac editions - when a victim opens a specially crafted document. The root cause (CWE-822) enables memory corruption through unvalidated pointer values sourced from attacker-controlled file content, yielding full confidentiality, integrity, and availability compromise of the targeted user session. No public exploit or active exploitation has been identified at time of analysis; a vendor-released patch is available through Microsoft Update channels.
Technical ContextAI
CWE-822 (Untrusted Pointer Dereference) describes a memory safety flaw where the application reads a pointer value from attacker-controlled input and dereferences it without bounds checking or type validation. In the Office context, document parsers routinely deserialize complex binary or XML-based structures; a crafted record can supply a fabricated pointer that, when followed, redirects code flow to attacker-supplied data and achieves arbitrary memory read/write. The CVSS vector AV:L reflects that exploitation occurs within the local process context upon file open, consistent with Office's COM-based parsing pipeline. ENISA EUVD-2026-56712 confirms the affected CPE spans Microsoft 365 Apps for Enterprise 16.0.x, Office 2019 19.0.x, Office LTSC 2021 16.0.x, Office LTSC 2024 16.0.x, Office LTSC for Mac 2021 16.0.x, Office LTSC for Mac 2024 16.0.x, and Office 365 for Mac 1.0.x.
RemediationAI
The primary remediation is to apply the vendor-released patch via Microsoft Update or the Microsoft 365 update channel as documented at https://aka.ms/OfficeSecurityReleases; macOS users must update to Office build 16.112.26081010 or later via Microsoft AutoUpdate. For organizations unable to patch immediately, enforcing Office Protected View via Group Policy (Computer Configuration > Administrative Templates > Microsoft Office > Security Settings > Protected View) reduces exposure by prompting users before rendering documents from untrusted sources - note that this may disrupt workflows relying on seamless file opens from shared drives or email attachments. Ensuring Mark of the Web (MOTW) propagation is intact for files downloaded from the internet further ensures Protected View triggers automatically for externally sourced documents; some archiving or EDR tools strip MOTW, which would negate this control. Refer to the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64910 for patch deployment guidance and channel-specific build verification.
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Same weakness CWE-822 – Untrusted Pointer Dereference
View allSame technique Authentication Bypass
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External POC / Exploit Code
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