crun, an OCI container runtime written in C, fails to open the container rootfs /dev directory without the O_NOFOLLOW flag before version 1.28. When an OCI bundle contains a symlink at rootfs/dev and the container configuration does not mount /dev, crun follows that symlink and creates default device nodes and stdio symlinks at the symlink target outside the container root filesystem. The result is that files on the host can be overwritten, for example the pre‑existing ptmx file can be replaced by crun’s forced ptmx → pts/ptmx symlink. Based on the description, it is inferred that an attacker who can craft a bundle with such a symlink could overwrite arbitrary host files, potentially leading to local privilege escalation or denial of service.

The affected product is crun, the open‑source OCI container runtime from containers:crun. All releases prior to version 1.28 are vulnerable. The fix was introduced in 1.28, so any crun runtime older than that must be updated before use.

The CVSS base score of 5.1 indicates moderate severity. No EPSS score is available, and the vulnerability is not listed in the CISA KEV catalog. The likely attack vector is a local rootful crun execution where the attacker controls the OCI bundle, based on the description. Because the flaw requires local access to the crun binary and the ability to craft a bundle with a dev symlink, the exploitation effort is moderate. Based on the description, a successful exploit would allow the attacker to create file system objects outside the container, potentially compromising host integrity or confidentiality.