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CVE-2026-96620

CRITICAL 9.2

Published 2026-10-16 · Last modified 2026-10-21

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.

ELEVATED IMPACT

Severe if exploited (CVSS 9.2), but no known exploitation and low modeled probability. Patch on a normal cadence.

Exploitation likelihood

0.7%chance of exploitation in 30 days · 53rd percentile

○ In CISA KEV ○ Catalogued PoC

Impact if exploited

9.2CVSS 4.0 · CRITICAL

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable
  • ⚠Requirements: Specific conditions must be present

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

Search for new PoCs

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Tracked sources are checked daily for recent CVEs, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Data snapshot:

Affected

Vendors Anthropics

Products Claude Agent Sdk Python

Weakness (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')

CVSS vector

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

References and research data (JSON)

Packages and version ranges

Each advisory describes its own package and affected ranges. A boundary applies to that range; it is not a universal upgrade recommendation.

  • claude-agent-sdk PyPI

    pkg:pypi/claude-agent-sdk

    ECOSYSTEM range
    • All earlier versions (introduced 0)
    • Fixed boundary (excluded): 0.2.121
    105 explicitly listed affected versions

    0.0.23, 0.1.0, 0.1.1, 0.1.10, 0.1.18, 0.1.19, 0.1.2, 0.1.20, 0.1.21, 0.1.22, 0.1.23, 0.1.25, 0.1.26, 0.1.27, 0.1.29, 0.1.3, 0.1.30, 0.1.31, 0.1.33, 0.1.34, 0.1.35, 0.1.36, 0.1.37, 0.1.38, 0.1.39, 0.1.4, 0.1.41, 0.1.43, 0.1.44, 0.1.45, 0.1.46, 0.1.47, 0.1.48, 0.1.49, 0.1.5, 0.1.50, 0.1.51, 0.1.52, 0.1.53, 0.1.54, 0.1.55, 0.1.56, 0.1.58, 0.1.59, 0.1.6, 0.1.60, 0.1.61, 0.1.62, 0.1.63, 0.1.64, 0.1.65, 0.1.66, 0.1.68, 0.1.69, 0.1.7, 0.1.70, 0.1.71, 0.1.72, 0.1.73, 0.1.74, 0.1.75, 0.1.76, 0.1.77, 0.1.78, 0.1.8, 0.1.80, 0.1.81, 0.1.9, 0.2.100, 0.2.101, 0.2.102, 0.2.103, 0.2.104, 0.2.105, 0.2.106, 0.2.107, 0.2.108, 0.2.109, 0.2.110, 0.2.111, 0.2.112, 0.2.113, 0.2.114, 0.2.115, 0.2.116, 0.2.117, 0.2.118, 0.2.119, 0.2.120, 0.2.82, 0.2.83, 0.2.84, 0.2.85, 0.2.86, 0.2.87, 0.2.88, 0.2.89, 0.2.90, 0.2.91, 0.2.93, 0.2.94, 0.2.95, 0.2.96, 0.2.97, 0.2.99

    Additional upstream package constraints
    {
  "database": {
    "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-h4mw-j7qp-8mwm/GHSA-h4mw-j7qp-8mwm.json"
  }
}
    GitHub Advisory Database · GHSA-h4mw-j7qp-8mwm · Updated 2026-10-16T20:00:04.101685566Z

All CVSS metrics

  • CRITICAL 9.2 v4.0 · CNA Primary
    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
  • CRITICAL 9.2 v4.0 · NVD Secondary
    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

References

Advisories

Technical & other

Sources: NVD · CVE.org · EPSS