{
  "schema_version": "1.6.0",
  "id": "ACVE-2026-0434",
  "aliases": [],
  "published": "2026-09-11T00:00:00Z",
  "modified": "2026-09-25T00:00:00Z",
  "summary": "Claude Code on macOS, opened on an untrusted repository with its sandbox enabled, ran a repository-controlled command outside the sandbox without a permission prompt.",
  "details": "## What\n\nAccomplish demonstrated that Claude Code's macOS sandbox covered the Bash tool while the harness's git path remained outside it. An untrusted repository could therefore cause a command to run with the logged-in user's authority even in the strictest permission mode.\n\n## Detection\n\nAccomplish includes a proof of concept and reports the fix in Claude Code 2.1.247.\n\n## Fix\n\nUpgrade Claude Code to 2.1.247 or later and do not treat the sandbox as a complete boundary for untrusted repositories.",
  "affected": [
    {
      "package": {
        "ecosystem": "AgentHarness",
        "name": "claude-code"
      },
      "ranges": [
        {
          "type": "SEMVER",
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.1.247"
            }
          ]
        }
      ]
    }
  ],
  "references": [
    {
      "type": "REPORT",
      "url": "https://accomplish.ai/blog/beltdown-escaping-the-claude-code-sandbox/"
    }
  ],
  "database_specific": {
    "severity": "HIGH",
    "acve": {
      "specVersion": 1,
      "status": "candidate",
      "kind": "code",
      "vulnClasses": [
        "sandbox-escape",
        "config-file-injection"
      ],
      "cwe": [
        "CWE-693"
      ],
      "taxonomy": {
        "owasp_asi": [
          "ASI05"
        ],
        "atlas": [
          "AML.T0105"
        ]
      },
      "cveBoundary": "pending-cve",
      "noCveReason": "No CVE was assigned in the public disclosure.",
      "exploitation": {
        "status": "demonstrated",
        "checkedAt": "2026-09-24T00:00:00Z",
        "sources": [
          {
            "url": "https://accomplish.ai/blog/beltdown-escaping-the-claude-code-sandbox/",
            "type": "research"
          }
        ],
        "kev": {
          "listed": false
        }
      },
      "fix": {
        "summary": "Upgrade Claude Code to 2.1.247 or later.",
        "actions": [
          {
            "type": "upgrade",
            "target": "harness:claude-code",
            "to": "2.1.247",
            "why": "Anthropic fixed the issue in this version according to the report.",
            "owner": "operator"
          }
        ]
      },
      "exposure": {
        "harness": {
          "value": "Claude Code below 2.1.247 on macOS",
          "any": false,
          "status": "confirmed",
          "source": "https://accomplish.ai/blog/beltdown-escaping-the-claude-code-sandbox/"
        },
        "model": {
          "value": "any",
          "any": true,
          "status": "unconfirmed"
        },
        "goal": {
          "value": "Any task opened in an untrusted repository",
          "stated": false,
          "status": "unconfirmed"
        },
        "tools": {
          "value": "The macOS sandboxed shell tool and the harness git path",
          "status": "confirmed",
          "source": "https://accomplish.ai/blog/beltdown-escaping-the-claude-code-sandbox/"
        },
        "approval": {
          "value": "Strict don't-ask mode still allowed the repository-controlled command to run outside the sandbox",
          "mode": "sandbox-escape",
          "status": "confirmed",
          "source": "https://accomplish.ai/blog/beltdown-escaping-the-claude-code-sandbox/"
        },
        "inputControl": "repo-author",
        "agentAction": "The harness runs a repository-controlled command outside the macOS sandbox.",
        "harm": "arbitrary-command",
        "divergence": "none",
        "reach": {
          "value": "The Mac and the logged-in user's files",
          "kinds": [
            "home-directory",
            "project-files"
          ],
          "status": "confirmed",
          "source": "https://accomplish.ai/blog/beltdown-escaping-the-claude-code-sandbox/"
        }
      },
      "reproducibility": {
        "status": "partial",
        "axesComplete": true,
        "componentsObtainable": null,
        "triggerPublished": false,
        "observableStated": true,
        "demonstrated": "researcher-demonstrated",
        "missing": [
          "vulnerable components are not confirmed obtainable",
          "trigger not published"
        ]
      }
    }
  }
}