CVE-2026-15921: nvm path traversal via a malicious mirror's LTS codename writes outside the alias directory

Node Version Manager (nvm) is a POSIX-compliant shell function for managing multiple node.js versions. In versions 0.32.1 through 0.40.5, nvm ls-remote (and other commands that refresh remote LTS aliases, such as nvm install --lts) parse the node.js mirror's index.tab and use each release's LTS codename field as an alias filename without validating it. A malicious, compromised, or man-in-the-middled mirror can return an LTS codename containing path-traversal sequences such as ../../../.bashrc, causing nvm to write the associated version string to a path outside $NVMDIR/alias. With the default layout ($NVMDIR is ~/.nvm), this can create or overwrite files in the user's home directory, including shell startup files, which can lead to code execution in a later shell session. Exploitation requires the victim to use a hostile mirror -- via a compromised mirror or CDN, a network man-in-the-middle, or a maliciously configured NVMNODEJSORGMIRROR/NVMIOJSORGMIRROR -- and to run an affected command. Version 0.40.6 validates remote LTS codenames as safe alias filenames and rejects .. path components when writing alias files.