Executive brief
runc, a widely used tool for managing Linux containers, contains a flaw in how it handles container images. A malicious image could trick the system into deleting specific files or creating unauthorized links on the host computer's file system. While the practical impact is limited because only specific filenames are affected, it could potentially lead to minor system instability or configuration errors. Users of Podman and containerd are primarily affected, while Docker users are protected by default security layers.
Technical details
A symlink following vulnerability exists in runc's setupPtmx and setupDevSymlinks functions. When setting up a container rootfs, these functions use filepath.Join on paths that may be influenced by a malicious /dev symlink in the container image. Because these operations occur before pivot_root(2), an attacker can trick runc into calling os.Remove or os.Symlink on host paths. This allows for the deletion of host files named 'ptmx' or the creation of a hardcoded set of symlinks (e.g., stdin, stdout, core) in arbitrary host directories. The vulnerability is mitigated in Docker due to its read-only layer masking, but affects other runtimes like Podman and containerd. Fixes are available in versions 1.3.6, 1.4.3, and 1.5.0-rc.3.
Affected products
- opencontainers runc < 1.3.6, >= 1.4.0-rc.1 < 1.4.3, >= 1.5.0-rc.1 < 1.5.0-rc.3
Timeline
- 2026-06-12: patched: Fix committed to repository
- 2026-06-13: advisory: GitHub Advisory GHSA-xjvp-4fhw-gc47 published
- 2026-07-01: disclosed: NVD publication date