CVEvulnerability

CVE-2026-96620

9.2 CRITICAL Published 2026-10-16 Modified 2026-10-21 Official page ↗
Status
Awaiting Analysis
Published
2026-10-16
Last modified
2026-10-21
Assigner
[email protected]
CVSS 4.0 ([email protected])
9.2 CRITICAL — CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weaknesses
CWE-20, CWE-78, CWE-88

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.

Related

Weakness · CWE (3)

  • CWE-20 Improper Input Validation weakness
  • CWE-78 Improper Neutralization of Special Elements used in an OS Command weakness
  • CWE-88 Improper Neutralization of Argument Delimiters in a Command weakness

References