CVE-2026-47766
MediumCVSS 5.1Summary
crun before version 1.28 contains a vulnerability in the default device setup that opens the container rootfs `/dev` directory without `O_NOFOLLOW`. If an OCI bundle contains `rootfs/dev` as a symlink and the bundle configuration does not mount `/dev`, crun follows that symlink and creates default device nodes and stdio symlinks at the symlink target outside the container rootfs. This can lead to overwriting existing files, such as ptmx.
Risk Assessment
A local attacker with root privileges can create device nodes or symlinks outside the rootfs, potentially leading to privilege escalation or system damage.
Recommendation
Upgrade crun to version 1.28 or later, which contains the fix.
Original NVD description (English source)
crun is an open source OCI Container Runtime fully written in C. Prior to version 1.28, crun's default device setup opens the container rootfs `/dev` directory without `O_NOFOLLOW`. If an OCI bundle contains `rootfs/dev` as a symlink and the bundle configuration does not mount `/dev`, crun follows that symlink and creates the default device nodes and stdio symlinks at the symlink target outside the container rootfs. In a local rootful crun replay, this created fixed device nodes and symlinks outside the rootfs before crun returned failure. A pre-existing file named `ptmx` in the target directory was also replaced by crun's forced `ptmx -> pts/ptmx` symlink. Version 1.28 fixes the issue.