nvm resolves a requested version or alias by treating it as a filename under $NVM_DIR/alias

Overview

nvm resolves a requested version or alias by treating it as a filename under $NVM_DIR/alias. Before 0.40.8, nvm_alias() 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. nvm_print_alias_file() 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.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.