Vulnerability in Microsoft 365 Word Copilot

CVE-2026-21521

Improper neutralization of escape, meta, or control sequences in Copilot allows an unauthorized attacker to disclose information over a network.

EPSS: 0.001 (31.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N/E:U/RL:O/RC:C.

Affected products

Microsoft 365 Word Copilot

Weakness classification (CWE)

CWE-150

References

Word Copilot Information Disclosure Vulnerability (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-21521?: CVE-2026-21521 is a high-severity vulnerability in Microsoft 365 Word Copilot, classified under CWE-150. CVSS score: 7.4/10. Published 2026-01-22.
How severe is CVE-2026-21521?: High severity. CVSS v3 base score is 7.4 out of 10.