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[ CVE-2026-96620 · Published 16 Oct 2026 ]

Claude Agent SDK: Argument Injection via resume Option Allows Arbitrary Command Execution

CVSS 9.2 EPSS <1%Fix available

[ Why it matters ]Priority signals

  • Critical severity: CVSS 9.2

[ Description ]Official description

Claude Agent SDK is a Python SDK for Claude Code. Prior to 0.2.121, the resume option is passed to the Claude CLI as a separate token without validation, so a dash-leading value is parsed as an independent CLI flag. An attacker can inject the --mcp-config flag to define a stdio MCP server, causing arbitrary command execution at CLI startup outside the SDK permission controls. The issue is exploitable when an application passes untrusted input as the session ID to resume. This issue is fixed in version 0.2.121.

[ Fixes ]Fixes and patches

  • claude-agent-sdk 0.2.121Fixed version · GitHub Advisories · pip package claude-agent-sdk: upgrade to 0.2.121 or later (affected < 0.2.121)

[ Packages ]Affected open-source packages

[ References ]References