CVE-2026-96620CWE-20CWE-78CWE-88command-injection

CVE-2026-96620

published October 17, 2026

CVSS
9.2
EPSS
1%
Percentile
46.8
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS
9.2 · NONE
CVSS v4.0
9.2 · 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
EPSS
0.00578 · 46.8th percentile
Weaknesses
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')
Published
2026-10-17T00:18Z
References (4)
https://github.com/anthropics/claude-agent-sdk-python/commit/347a1cb88d7652199399db1b7f914e0a459a6662 · [email protected]https://github.com/anthropics/claude-agent-sdk-python/pull/1123 · [email protected]https://github.com/anthropics/claude-agent-sdk-python/releases/tag/v0.2.121 · [email protected]https://github.com/anthropics/claude-agent-sdk-python/security/advisories/GHSA-h4mw-j7qp-8mwm · [email protected]
EPSS history
Timeline
  • 18 OCT 03:33Z
    EPSS moved — → 1%
    epss
  • 16 OCT 19:44Z
    Claude Agent SDK: Argument Injection via resume Option Allows Arbitrary Command Execution
    cvelistv5
  • 16 OCT 19:44Z
    Claude Agent SDK: Argument Injection via resume Option Allows Arbitrary Command Execution
    cvelistv5