CVE-2026-21521

HIGHNVD 7.47.4—Trending — 4 sources updated this week

7.4

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

CVSS v3: 7.4
EG Score: 7.4(medium)
EPSS: 31.2%
KEV: Not listed

Published

January 22, 2026

Last Modified

February 2, 2026

References (1)

secure@microsofthttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21521

Vendor Advisories for CVE-2026-21521(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

CVE-2026-21521
Microsoft Security Response Center (MSRC)Critical
Word Copilot Information Disclosure Vulnerability

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-150

Data Freshness Timeline

(refreshed 15× in last 7d / 15× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-06-02 20:13 UTCepss_batch
2026-06-02 20:13 UTCepss_batch
2026-06-01 13:51 UTCepss_batch
2026-06-01 13:51 UTCepss_batch
2026-06-01 13:51 UTCepss_batch
2026-05-31 22:30 UTCepss_batch
2026-05-31 22:30 UTCepss_batch
2026-05-31 00:16 UTCepss_batch
2026-05-31 00:16 UTCepss_batch
2026-05-31 00:16 UTCepss_batch
2026-05-29 15:23 UTCEG score recompute
2026-05-29 15:23 UTCVendor advisory
2026-05-29 15:23 UTCGHSA enrichment
2026-05-29 13:44 UTCepss_batch
2026-05-29 13:44 UTCepss_batch

Frequently asked(5)

What is CVE-2026-21521?

CVE-2026-21521 is a high vulnerability published on January 22, 2026. Improper neutralization of escape, meta, or control sequences in Copilot allows an unauthorized attacker to disclose information over a network.

When was CVE-2026-21521 disclosed?

CVE-2026-21521 was first published in the National Vulnerability Database on January 22, 2026, with the most recent update on February 2, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2026-21521 actively exploited?

CVE-2026-21521 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 31.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2026-21521?

CVE-2026-21521 has a CVSS v3 base score of 7.4 (NVD).

How do I remediate CVE-2026-21521?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-21521, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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CVE-2026-21521

📅 Published

🔄 Last Modified

🔗 References (1)

📣 Vendor Advisories for CVE-2026-21521(1)