---
id: "CVE-2026-118905"
kind: "vulnerability"
aliases: ["CVE-2026-118905"]
title: "nvm: crafted version string or .nvmrc runs shell commands as user"
severity: "high"
cvss: 7.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["ci", "developer-workstations", "node.js", "nvm", "package", "shell"]
not_affected_if: ["no-auto-switch-hook", "no-untrusted-nvmrc", "version-0.40.6-or-later"]
published_at: "2026-10-29T06:17:20+00:00"
first_seen_at: "2026-10-29T06:53:13+00:00"
updated_at: "2026-10-29T06:54:30+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118905", "first_seen_at": "2026-10-29T06:53:13+00:00"}]
---

# nvm: crafted version string or .nvmrc runs shell commands as user

Versions 0.31.2 through 0.40.5 of nvm build a sed program from the requested version string without escaping backslashes, so a '#' in that string lets an attacker inject sed commands. With GNU sed this runs a shell command as the user; with BSD sed it can read and write files.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `nvm --version` and check whether it falls in 0.31.2 through 0.40.5.
- Check whether a bash `cdnvm` or zsh `load-nvmrc` hook is installed in shell startup files, since those read `.nvmrc` files automatically.
- Check whether scripts run `nvm use "$(cat .nvmrc)"` on untrusted repositories.

## Timeline

- 2026-10-29T06:53:13+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118905

## From the sources

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, `nvm_ls` 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 `NODE_VERSION`, 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.

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