GHSA-h4mw-j7qp-8mwm
Claude Agent SDK: Argument Injection via resume Option Allows Arbitrary Command Execution
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| PyPI | claude-agent-sdk | < 0.2.121 | 0.2.121 |
Details
As written in the advisory (Markdown source, shown as plain text).
The Claude Agent SDK for Python passed the `resume` option to the Claude CLI without validation, allowing a value beginning with `-` to be interpreted as a separate CLI flag. An attacker who controlled the `resume` value could inject an `--mcp-config` flag defining a stdio MCP server, resulting in arbitrary command execution at CLI startup that bypassed the SDK's permission controls. Exploitation required an application to pass untrusted input as the session ID to resume.
Users are advised to update to the latest version of the claude-agent-sdk package.
Thank you to hackerone.com/moamenmahmood for reporting this issue.
References
External links from the advisory. They lead to third-party sites.
- https://github.com/anthropics/claude-agent-sdk-python/security/advisories/GHSA-h4mw-j7qp-8mwm
- https://github.com/anthropics/claude-agent-sdk-python/pull/1123
- https://github.com/anthropics/claude-agent-sdk-python/commit/347a1cb88d7652199399db1b7f914e0a459a6662
- https://github.com/anthropics/claude-agent-sdk-python
- https://github.com/anthropics/claude-agent-sdk-python/releases/tag/v0.2.121