runc: Malicious image with /dev symlink can trigger limited host filesystem integrity violations

Summary

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.

Timeline

1. Jul 1, 2026, 12:02 AM UTCCVE published
2. Jul 1, 2026, 1:34 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Jul 1, 2026, 1:35 PM UTCRecord last updated

Affected versions

• opencontainers runc

  fixed in 1.3.6; From 1.4.0-rc.1 · fixed in 1.4.3; From 1.5.0-rc.1 · fixed in 1.5.0-rc.3

• github.com/opencontainers/runcGo

  fixed in 1.3.6

• github.com/opencontainers/runcGo

  From 1.4.0 · fixed in 1.4.3

• github.com/opencontainers/runcGo

  From 1.5.0-rc.1 · fixed in 1.5.0-rc.3

• github.com/opencontainers/runcGo

  fixed in 1.3.6; From 1.4.0 · fixed in 1.4.3; From 1.5.0-rc.1 · fixed in 1.5.0-rc.3

References 2