Summary
Impact: Remote Code Execution. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
How could an attacker exploit this vulnerability?
The AV:N rating indicates the vulnerability is exploitable over the network, meaning an attacker can deliver a malicious prompt remotely without prior access, while UI:R means a user must interact with Copilot for exploitation to occur. Due to prompt injection, the system is coerced into executing attacker-controlled instructions, which can escalate into remote code execution (RCE) when the compromised prompt causes backend components or integrated tools to run unintended commands.
Security updates
17.14.26 — https://learn.microsoft.com/en-us/visualstudio/releases/2022/release-notes
18.3.0 — https://learn.microsoft.com/en-us/visualstudio/releases/2026/release-notes
Vulnerabilities 1
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High 8.8
GitHub Copilot and Visual Studio Remote Code Execution Vulnerability
Improper neutralization of special elements used in a command ('command injection') in GitHub Copilot and Visual Studio allows an unauthorized attacker to execute code over a network.
Revision history
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#3
Changes made to the security updates links and information. This is an informational change only.
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#2
Changes made to the security updates links and information. This is an informational change only.
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#1
Information published.
References
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CVE-2026-21256 GitHub Copilot and Visual Studio Remote Code Execution Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21256
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss