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Vulnerability details

CVE-2026-96620

anthropics claude-agent-sdk-python

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

CVSS 4.0
9.2Critical

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.

CVSS scores

ScoreVersionSourceVector
9.2Critical 4.0 CVEProject cvelistV5 (CNA) (GitHub_M) 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

Affected products

VendorProductVersionsSource
anthropics claude-agent-sdk-python < 0.2.121 CVEProject cvelistV5 (CNA)

References and advisories

4
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Details

Published
2026-10-16
Last updated
2026-10-22
State
Published
Assigner (CNA)
GitHub_M
Kolun priority
27 · Low

Exploit prediction (EPSS)

0.7%
Probability of exploitation in 30 days
53.5%
Percentile (among all CVEs)

SSVC assessment (CISA)

Automatable
Yes
Exploitation
None
Technical impact
Total

Weaknesses (CWE)

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