What is CVE-2026-21523?

CVE-2026-21523 is a high-severity vulnerability in Microsoft Visual Studio Code Copilot Chat Extension, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 8.0/10. Published 2026-02-10.

How severe is CVE-2026-21523?

High severity. CVSS v3 base score is 8.0 out of 10.

Vulnerability in Microsoft Visual Studio Code Copilot Chat Extension

CVE-2026-21523

Time-of-check time-of-use (toctou) race condition in GitHub Copilot and Visual Studio allows an authorized attacker to execute code over a network.

Vulnerability class: TOCTOU (Time-of-Check to Time-of-Use)

EPSS: 0.000 (10.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.0 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C.

Affected products

Microsoft Visual Studio Code Copilot Chat Extension — versions 0.27.0
Microsoft Visual Studio Code — versions 1.0.0

Weakness classification (CWE)

CWE-367 — Time-of-check Time-of-use (TOCTOU) Race Condition

References

GitHub Copilot and Visual Studio Code Remote Code Execution Vulnerability (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-21523?: CVE-2026-21523 is a high-severity vulnerability in Microsoft Visual Studio Code Copilot Chat Extension, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 8.0/10. Published 2026-02-10.
How severe is CVE-2026-21523?: High severity. CVSS v3 base score is 8.0 out of 10.