Critical Docker Sandboxes Vulnerabilities Patched

TL;DR

Docker issued a patch for critical Docker Sandboxes vulnerabilities, including CVE-2026-77179 and CVE-2026-79994. These flaws enable malicious guests to escape isolated microVM workspaces and interact with the host system. Administrators must update to version 0.42.0 immediately to prevent potential host code execution.

Why It Matters

Developers use Docker Sandboxes to run AI coding agents inside isolated environments. These sandboxes utilize dedicated Docker daemons and filesystems. Consequently, these Docker Sandboxes vulnerabilities expose the underlying host infrastructure to severe risks. If an attacker breaches the microVM, they can manipulate host files or access restricted capabilities. A compromised host could lead to widespread enterprise network infiltration.

How the Attack Works

The first flaw, CVE-2026-77179, involves the virtio-fs host server on macOS. The server improperly follows symlinks when reopening unlinked files. A malicious guest can replace a parent directory with a symlink. This action allows the guest to escape the shared workspace. The attacker can then modify arbitrary host files as the VMM user.

The second vulnerability, CVE-2026-79994, affects the guest-to-host Unix domain socket relay. The relay verifies that a socket path resides inside an authorized workspace. However, the system reconnects using the original path name. A malicious guest can exploit this time delay. They can replace an intermediate directory with a symlink before the connection occurs. This forces the host to connect to an arbitrary AF_UNIX socket outside the shared space. Currently, no active in-the-wild exploitation or public proof-of-concept exists for these flaws.

Affected Versions

CVE-2026-77179 affects macOS versions from 0.28.0 up to, but not including, 0.42.0. Meanwhile, CVE-2026-79994 impacts versions 0.37.0 up to, but not including, 0.42.0 across platforms.

Patch and Mitigation Steps

Users must upgrade immediately to remediate these Docker Sandboxes vulnerabilities. Docker addressed these issues in the 0.42.0 security update. If updating is impossible, administrators should run sandboxes in clone mode. Additionally, they must avoid adding read-write host mounts to the sandbox configuration.

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Written by

@DdoS · Security Researcher

Do Son

Do Son is the Founder and Editor of SecurityOnline.info. Working in cybersecurity since 2013, he reports on vulnerabilities, malware, and emerging threats, providing timely analysis to help organizations and individuals stay ahead of evolving risks.