uutils mkfifo Flaw Exposes Sensitive Files to Permission Changes

A critical vulnerability, CVE-2026-35341, exists within the uutils coreutils mkfifo utility, as detailed by the National Vulnerability Database. This flaw enables unauthorized modification of permissions on pre-existing files. The issue arises when mkfifo fails to create a FIFO because a file already occupies the target path; instead of terminating, it proceeds to execute a set_permissions call.

This oversight results in the existing file’s permissions being reset to a default mode, frequently 644 after umask application. The National Vulnerability Database warns that this could expose highly sensitive data, such as SSH private keys, to other unauthorized users on the system. The vulnerability carries a CVSS score of 7.1 (HIGH), indicating a significant risk to confidentiality and integrity.

For defenders, this is a clear operational security issue. The attacker’s calculus is simple: exploit a common utility’s error handling to achieve privilege escalation or lateral movement by exposing critical credentials. CISOs must understand that this isn’t about arbitrary code execution, but about undermining fundamental file system security. It’s a silent permission change that can open the door to far more damaging attacks.