CVE-2026-21514: Microsoft Office Word Reliance on Untrusted Inputs in a Security Decision Vulnerability

What it is

Reliance on untrusted inputs in a security decision in Microsoft Office Word allows an unauthorized attacker to bypass a security feature locally.

Exploitation evidence

First exploit evidence seen: 2026-02-10 (earliest date across the sources below).

Exploited in the wild

• CISA KEV: listed since 2026-02-10. Source

Public exploit code

GitHub proof-of-concept repositories below quality bar

1 public repositories from 1 accounts, first seen 2026-05-04.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: CISA KEV · nomi-sec/PoC-in-GitHub.

How to fix it

CISA required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. (source: CISA KEV)

Fixed versions

NVD does not list a fixed version for this CVE. Use the vendor advisory below.

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21514 (CISA KEV notes)

Detection Generic guidance

Response checklist Generic guidance

1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.