---
id: CVE-2026-121751
title: >-
  nvm evaluates a malicious mirror's index.tab version strings as shell
  arithmetic via stored LTS aliases
summary: >-
  Node Version Manager (nvm) is a POSIX-compliant shell function for managing
  multiple node.js versions. In versions 0.39.6 through 0.40.8, `nvm ls-remote`
  (and other commands that refresh remote LTS aliases) store the version column
  of th…
severity: low
cvss: 3.1
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N'
cvssSource: cna
cwe:
  - CWE-78
  - CWE-20
vendor: nvm-sh
product: nvm
affected:
  - nvm >= 0.39.6 < 0.41.0
published: '2026-11-04'
updated: '2026-11-04'
sourceUpdated: '2026-11-04T21:26:57.967Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-121751'
references:
  - url: 'https://github.com/nvm-sh/nvm/security/advisories/GHSA-7prg-rw9c-82h7'
    label: GHSA-7prg-rw9c-82h7
  - url: >-
      https://github.com/nvm-sh/nvm/commit/aa0572b7c48b2652a9f86276bbbf3840939981af
    label: Fix commit aa0572b7
tags:
  - cve.org
ingestedAt: '2026-11-05T21:36:00.613Z'
---

## Overview

Node Version Manager (nvm) is a POSIX-compliant shell function for managing multiple node.js versions. In versions 0.39.6 through 0.40.8, `nvm ls-remote` (and other commands that refresh remote LTS aliases) store the version column of the mirror's `index.tab` in `$NVM_DIR/alias/lts/` without validating it, and `nvm_normalize_lts` later evaluates any suffix of an `lts/-N` value inside shell arithmetic `$((N+1))`. Under bash and zsh, arithmetic evaluation expands command substitutions in array subscripts, so a stored value such as `lts/-10*path[$(cmd)1]` runs `cmd` as the user when the alias is later resolved by purely local commands (`nvm ls`, `nvm alias`, `nvm use --lts`, `nvm which lts/`), and in every new shell when the `default` alias is `lts/*`. Exploitation requires the victim to use a hostile mirror -- via a compromised mirror or CDN, a network man-in-the-middle of an `http://` mirror, or a maliciously configured `NVM_NODEJS_ORG_MIRROR` -- and to run an affected command. The same sink is also reachable from a project `.nvmrc`, which is treated as hardening. dash is not affected. Version 0.41.0 only passes an all-digit `lts/-N` offset to arithmetic and drops `index.tab` rows whose version is not a valid version string.

## Affected

- `nvm >= 0.39.6 < 0.41.0`

## Remediation

Upgrade to nvm 0.41.0 or later, which only lets an all-digit `lts/-N` offset reach shell arithmetic and drops mirror rows with invalid version strings. (Only needed if using a non-default mirror whose metadata contents you do not trust, or running nvm in untrusted project directories.)

### Workarounds

Until upgrading, only run `nvm ls-remote` and LTS-refreshing commands against trusted mirrors over TLS, ensure `NVM_NODEJS_ORG_MIRROR` points only at a trusted endpoint, and do not run nvm in untrusted project directories.