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Vulnerability details: VCID-nhuu-v424-ebcz
Vulnerability ID VCID-nhuu-v424-ebcz
Aliases CVE-2026-29783
GHSA-g8r9-g2v8-jv6f
Summary The shell tool within GitHub Copilot CLI versions prior to and including 0.0.422 can allow arbitrary code execution through crafted bash parameter expansion patterns. An attacker who can influence the commands executed by the agent (e.g., via prompt injection through repository files, MCP server responses, or user instructions) can exploit bash parameter transformation operators to execute hidden commands, bypassing the safety assessment that classifies commands as "read-only." This has been patched in version 0.0.423. The vulnerability stems from how the CLI's shell safety assessment evaluates commands before execution. The safety layer parses and classifies shell commands as either read-only (safe) or write-capable (requires user approval). However, several bash parameter expansion features can embed executable code within arguments to otherwise read-only commands, causing them to appear safe while actually performing arbitrary operations. The specific dangerous patterns are ${var@P}, ${var=value} / ${var:=value}, ${!var}, and nested $(cmd) or <(cmd) inside ${...} expansions. An attacker who can influence command text sent to the shell tool - for example, through prompt injection via malicious repository content (README files, code comments, issue bodies), compromised or malicious MCP server responses, or crafted user instructions containing obfuscated commands - could achieve arbitrary code execution on the user's workstation. This is possible even in permission modes that require user approval for write operations, since the commands can appear to use only read-only utilities to ultimately trigger write operations. Successful exploitation could lead to data exfiltration, file modification, or further system compromise.
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
Affected and Fixed Packages Package Details
Weaknesses (3)
CWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
epss 0.00065 https://api.first.org/data/v1/epss?cve=CVE-2026-29783
cvssv3.1_qr HIGH https://github.com/advisories/GHSA-g8r9-g2v8-jv6f
cvssv4 7.5 https://github.com/github/copilot-cli
generic_textual HIGH https://github.com/github/copilot-cli
cvssv4 7.5 https://github.com/github/copilot-cli/releases/tag/v0.0.423
generic_textual HIGH https://github.com/github/copilot-cli/releases/tag/v0.0.423
ssvc Track* https://github.com/github/copilot-cli/releases/tag/v0.0.423
cvssv3.1_qr HIGH https://github.com/github/copilot-cli/security/advisories/GHSA-g8r9-g2v8-jv6f
cvssv4 7.5 https://github.com/github/copilot-cli/security/advisories/GHSA-g8r9-g2v8-jv6f
generic_textual HIGH https://github.com/github/copilot-cli/security/advisories/GHSA-g8r9-g2v8-jv6f
ssvc Track* https://github.com/github/copilot-cli/security/advisories/GHSA-g8r9-g2v8-jv6f
cvssv4 7.5 https://nvd.nist.gov/vuln/detail/CVE-2026-29783
generic_textual HIGH https://nvd.nist.gov/vuln/detail/CVE-2026-29783
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2026-29783
https://github.com/github/copilot-cli
CVE-2026-29783 https://nvd.nist.gov/vuln/detail/CVE-2026-29783
GHSA-g8r9-g2v8-jv6f https://github.com/advisories/GHSA-g8r9-g2v8-jv6f
GHSA-g8r9-g2v8-jv6f https://github.com/github/copilot-cli/security/advisories/GHSA-g8r9-g2v8-jv6f
v0.0.423 https://github.com/github/copilot-cli/releases/tag/v0.0.423
No exploits are available.
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N Found at https://github.com/github/copilot-cli
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

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Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N Found at https://github.com/github/copilot-cli/releases/tag/v0.0.423
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

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Vector: SSVCv2/E:P/A:N/T:T/P:M/B:A/M:M/D:R/2026-03-06T18:05:42Z/ Found at https://github.com/github/copilot-cli/releases/tag/v0.0.423
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N Found at https://github.com/github/copilot-cli/security/advisories/GHSA-g8r9-g2v8-jv6f
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

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Vector: SSVCv2/E:P/A:N/T:T/P:M/B:A/M:M/D:R/2026-03-06T18:05:42Z/ Found at https://github.com/github/copilot-cli/security/advisories/GHSA-g8r9-g2v8-jv6f
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N Found at https://nvd.nist.gov/vuln/detail/CVE-2026-29783
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

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present

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passive

active

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Exploit Prediction Scoring System (EPSS)
Percentile 0.20388
EPSS Score 0.00065
Published At June 11, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-06-11T16:46:51.750397+00:00 Vulnrichment Import https://github.com/cisagov/vulnrichment/blob/develop/2026/29xxx/CVE-2026-29783.json 38.6.0