runc is a CLI tool for spawning and running containers according to the OCI specification. In versions prior to 1.3.6, 1.4.0-rc.1, 1.4.0-rc.12, 1.5.0-rc.1, and 1.5.0-rc.1, when setting up the container rootfs, setupPtmx and setupDevSymlinks call os.Remove and os.Symlink with a filepath.Join string which allow an image with /dev as a symlink to trick runc into deleting files called ptmx on the host or creating a hardcoded set of symlinks with specific names and targets in an arbitrary pre-existing host directory. This issue is not exploitable under Docker, because Docker creates a top-level read-only layer that masks any malicious /dev symlink present in the container image — unlike some other Linux container tooling, whose higher-level runtimes built on runc remain exposed to exploitation via a malicious image. This issue has been fixed in versions 1.3.6, 1.4.3 and 1.5.0.
CVSS Details
- CVSS 3.1 Base Score: 3.3
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Alpine Linux | — | Upgrade runc | Jul 2, 2026 | Jul 1, 2026 |
| Redhat_linux | — | No solution exists | Jul 29, 2026 | Jul 1, 2026 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Aug 13, 2026 | Jul 1, 2026 |
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