Node Version Manager (nvm) is a POSIX-compliant shell function for managing multiple node.js versions. In versions 0.31.2 through 0.40.5, nvmls filters installed versions with a sed program that embeds the requested version pattern in a \#...# address, escaping . (and, since 0.40.4, #) but not backslash. A version string containing # (or \#) therefore closes the address early, and the rest of it is parsed as sed commands: with GNU sed, the e command runs a shell command as the user; with BSD sed, the w and r commands write and read files. This is reachable whenever an attacker-influenced version string is passed to nvm use, nvm which, nvm ls, nvm version, nvm run, or nvm exec, or to nvm-exec via NODEVERSION, and at least one version is installed. nvm's own .nvmrc parser strips comments, so a bare nvm use is not affected; however, the bash cdnvm and zsh load-nvmrc auto-switch hooks documented in the README read .nvmrc as-is and pass it to nvm ls and nvm version, so a user with one of those hooks installed runs the attacker's command just by changing into a directory under a malicious .nvmrc; scripts that run nvm use "$(cat .nvmrc)" are affected the same way. Version 0.40.6 passes any version pattern containing # or a newline through the .nvmrc content parser first, so no # reaches the sed program.

nvm resolves a requested version or alias by treating it as a filename under $NVMDIR/alias. Before 0.40.8, nvmalias() concatenated the requested name onto that directory and read the result with no containment check, so a name containing a .. component escaped the alias directory; under the default layout an alias such as ../../.npmrc resolves to a file in the user's home directory. nvmprintaliasfile() then emits every non-comment, non-empty line of whatever was opened. A version string taken from an untrusted .nvmrc reaches this path, so a developer who runs nvm use, nvm install, or nvm which inside an attacker-supplied repository discloses the first non-comment line of an arbitrary file readable by that user, in the resulting "is not yet installed" error message. A user-supplied nvm alias <traversing-name> discloses every non-comment line of the target file. There is no integrity or availability impact, and no command execution on this path.

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.