What is CVE-2025-66389?

CVE-2025-66389 is a high-severity vulnerability in Microsoft GitHub Copilot, classified under Files or Directories Accessible to External Parties. CVSS score: 7.5/10. Published 2026-06-22.

How severe is CVE-2025-66389?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Microsoft GitHub Copilot

CVE-2025-66389

GitHub Copilot 1.372.0 allows filesystem access outside of a workspace folder (without user approval) via a file-handler URI parameter to fetch_webpage. Therefore, exfiltration could occur if there is indirect prompt injection.

Published 2026-06-22 · last modified 2026-06-30.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.012 (66.3th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 66th percentile — 66.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.012 · change: 0.000

Affected products

Microsoft GitHub Copilot — versions 1.372.0

Weakness classification (CWE)

CWE-552 — Files or Directories Accessible to External Parties

References

github.com/microsoft/vscode-copilot-chat/ (Product)
github.com/microsoft/vscode/blob/03baef1008086ed4960042fa463e570072173bb5/src/v… (Product)
blindcyber.com/2025/10/28/copilot-fun/ (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2025-66389?: CVE-2025-66389 is a high-severity vulnerability in Microsoft GitHub Copilot, classified under Files or Directories Accessible to External Parties. CVSS score: 7.5/10. Published 2026-06-22.
How severe is CVE-2025-66389?: High severity. CVSS v3 base score is 7.5 out of 10.