GNU cpio’s tar extraction routine sanitizes file names but omits sanitation for hard‑link targets when the --no-absolute-filenames option is used. An archive supplied by an attacker that contains a hard‑link entry with a linkname pointing to an absolute path outside the extraction directory causes cpio to create a hard link to that external file. This bypasses the intended restriction and allows the attacker to create or expose a link to any file that cpio can reach with its current permissions, potentially enabling the attacker to read or modify that file through the newly created link.

The vulnerability affects all GNU cpio versions prior to the revision identified by commit e2b9cbdd3354d2b1569b7390d1bc15c1930559ad. Systems running older releases of the cpio utility—regardless of the operating system—are impacted.

The CVSS score of 4.6 indicates moderate complexity and scope; the exploit requires the ability to provide a crafted tar file to a running instance of cpio. Because the attack relies on local access to cpio, it is most relevant to users with local privileges and is not listed in the CISA KEV catalog. No EPSS data is available, suggesting that the exploit probability is not well characterized yet. Given the lack of known public exploitation, the risk is considered moderate, but any system that processes untrusted archives with cpio should treat this as a potential threat.