GitHub copilot-cli up to 0.0.422 os command injection

Summaryinfo

A vulnerability classified as critical has been found in GitHub copilot-cli up to 0.0.422. The affected element is an unknown function. Performing a manipulation results in os command injection. This vulnerability is cataloged as CVE-2026-29783. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in GitHub copilot-cli up to 0.0.422. This affects some unknown processing. The manipulation with an unknown input leads to a os command injection vulnerability. CWE is classifying the issue as CWE-78. The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-29783 since 03/04/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1202 for this issue.

Upgrading to version 0.0.423 eliminates this vulnerability. The upgrade is hosted for download at github.com.

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Productinfo

Type

• Bug Tracking Software

Vendor

• GitHub

Name

• copilot-cli

Version

• 0.0.422

License

• open-source

Website

• Product: https://github.com/github/copilot-cli/

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