---
id: "CVE-2026-103916"
kind: "vulnerability"
aliases: ["CVE-2026-103916"]
title: "Docker Sandboxes sbx cp lets a sandbox escape its shared workspace"
severity: "high"
cvss: 8.4
epss: null
exploited: false
status: "open"
category: "other"
products: [{"name": "Docker Sandboxes (sbx)", "fixed": ["0.51.0"], "affected": ">= 0.28.0, < 0.51.0", "ecosystem": "vendor"}]
ecosystems: []
tags: ["docker", "docker-sandboxes", "other", "sbx"]
not_affected_if: ["sbx-cp-unused"]
published_at: "2026-11-03T17:17:52+00:00"
first_seen_at: "2026-11-03T17:21:54+00:00"
updated_at: "2026-11-03T17:28:08+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-103916", "first_seen_at": "2026-11-03T17:21:54+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-11-03T17:28:08+00:00"}]
---

# Docker Sandboxes sbx cp lets a sandbox escape its shared workspace

Docker Sandboxes' sbx cp command does not keep host-side paths confined to the shared workspace. A malicious sandbox can plant a symlink so a later user-initiated copy reads or writes host files outside the workspace, using the invoking user's permissions.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Docker Sandboxes (sbx) affected >= 0.28.0, < 0.51.0 fixed 0.51.0

## How to check

- Run `sbx version`; versions from 0.28.0 up to but not including 0.51.0 are in the affected range reported in the CVE record (as relayed by hol.org; Docker's release notes do not name the CVE).
- Only matters if you run `sbx cp` against a sandbox you do not fully trust. Before upgrading, avoid `sbx cp` on sandboxes that may be compromised and check the workspace for unexpected symlinks pointing outside it.

## Fix

Upgrade Docker Sandboxes (sbx) to 0.51.0 or later; 0.51.0 release notes: 'sbx cp blocks symbolic links in mounted directories from escaping onto other host paths.'

## Timeline

- 2026-11-03T17:21:54+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-103916
- 2026-11-03T17:28:08+00:00 analyst — Fix 0.51.0 confirmed in Docker release notes (sbx cp symlink item, released 3 Nov) but notes do not cite the CVE; affected range >=0.28.0 <0.51.0 comes from CVE record via hol.org rewrite, so nothing marked verified. v0.50.0 partly hardened sbx cp (alternate host path symlinks) but is not the fix. No exploitation or PoC found; no social search done.

## Documents

- [fix] Release notes: github.com https://github.com/docker/sbx-releases/releases/tag/v0.51.0

## From the sources

Docker Sandboxes sbx cp does not safely confine host-side paths to a shared workspace. A malicious sandbox can create or replace a workspace symlink so that a later user-initiated copy reads a host file outside the workspace into the sandbox or writes sandbox-controlled data to a host path outside the workspace with the invoking user's permissions.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_