CVE-2026-96620

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

At a glance

Severity: CRITICAL 9.2
EPSS: EPSS 0.70 % · percentile 53 (2026-10-27)
State: PUBLISHED
Published: 2026-10-16
Updated: 2026-10-21
Assigner: GitHub_M
NVD status: Awaiting Analysis

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.

Scores

Version	Score	Vector	Scored by
CVSS 4.0	CRITICAL 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	GitHub_M
CVSS 4.0	CRITICAL 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/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	NVD · security-advisories@github.com (Secondary)

Weaknesses (CWE)

Advisories

GHSA-h4mw-j7qp-8mwm — Claude Agent SDK: Argument Injection via resume Option Allows Arbitrary Command Execution

European references

ENISA EUVD · EUVD-2026-103155
GCVE · GCVE-0-2026-96620

Affected products

Product	Versions
anthropics · claude-agent-sdk-python	affected < 0.2.121

References

Sources

Source	Licence
CVE List (CVEProject cvelistV5)	CVE Program Terms of Use
EPSS (FIRST.org)	FIRST — attribution requested
ENISA EUVD	ENISA — reproduction authorised, source acknowledged
NVD (NIST) via fkie-cad/nvd-json-data-feeds	Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD