CVE-2026-12539

On macOS, the virtio-fs host server used by Docker Sandboxes improperly follows symlinks when reopening an unlinked file from a stored path. A malicious guest can replace a parent directory with a symlink, escape the shared workspace, and read or modify arbitrary host files as the VMM user, potentially achieving host code execution.

Docker Sandboxes compared OAuth token-endpoint hostnames case-sensitively when deciding whether to mask managed credential responses, while request routing treated DNS hostnames case-insensitively. Untrusted code inside a sandbox could use a case-variant hostname to reach the genuine provider endpoint while bypassing response masking. If a user completed the OAuth flow, the provider's access and refresh tokens could be returned unmasked to the sandbox, exposing host-managed credentials.

Docker Sandboxes could forward a client-supplied credential alongside a credential injected by the host egress proxy. The proxy removed alternate credentials only when their values matched known sentinel values, so untrusted code in an authorized sandbox could supply an unrecognized credential in another supported authentication header. For affected upstream services, this could authenticate the request to an attacker-controlled account and expose data included in the request.

Docker Sandboxes could fail open while masking credentials in protected proxy responses. When a response-body read returned data together with an error, affected handlers could forward unmasked bytes. Code inside an authorized sandbox could use this to recover host-managed OAuth access and refresh tokens or a derived Anthropic API key intended to remain outside the sandbox.

The guest-to-host Unix-domain socket relay in Docker Sandboxes validates that a socket path is inside an authorized workspace, but later reconnects using the pathname. A malicious guest can replace an intermediate directory with a symlink between validation and connection, causing the host to connect to an arbitrary AF_UNIX socket outside the shared workspace. This can expose data or host-side capabilities provided by the targeted socket.

Docker Sandboxes (sbx) applies the read-only intent of a runtime host mount to the in-guest container bind only: the underlying virtio-fs host-edge grant is added to the sandbox's policy-share allowlist with no access mode. The directory stays writable at its shared-export path, so unprivileged code inside the sandbox can derive that path and write to a host directory the operator attached read-only.

A vulnerability in Docker Sandboxes (sbx) allows bypassing the HTTP/S-only egress allowlist via DNS tunneling. The embedded DNS server forwards queries to the host resolver without policy enforcement, enabling untrusted workloads to exfiltrate data encoded in DNS labels.