GHSA-g8r9-g2v8-jv6f · Severity: high · Ecosystem: npm — GitHub Copilot CLI Dangerous Shell Expansion Patterns Enable Arbitrary Code Execution
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.
Conclusion & alert: CVE-2026-29783 is rated Exploit Available (53/100): CVSS High severity, with low exploitation likelihood (EPSS 0.08%). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
| EDB-ID | Source | Kind | Published | Link |
|---|---|---|---|---|
| — | nvd_ref | exploit_tag | Exploit-DB ↗ |
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-03-07 | — | 0.08% | — |
Full EPSS history (1 record total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 7.5 | 4.0 | HIGH |
|
— | — | [email protected] |
| 7.8 | 3.1 | HIGH |
|
1.8 | 5.9 | [email protected] |
GHSA-g8r9-g2v8-jv6f · Severity: high · Ecosystem: npm — GitHub Copilot CLI Dangerous Shell Expansion Patterns Enable Arbitrary Code Execution
| Vendor | Product | Version | Raw CPE |
|---|---|---|---|
| github | copilot_command_line_interface | < 0.0.423 | cpe:2.3:a:github:copilot_command_line_interface:*:*:*:*:*:*:*:* |
| URL | Tags |
|---|---|
| https://github.com/github/copilot-cli/releases/tag/v0.0.423 | Release Notes |
| https://github.com/github/copilot-cli/security/advisories/GHSA-g8r9-g2v8-jv6f | Exploit Vendor Advisory |