CVE-2026-121751 nvm evaluates a malicious mirror's index.tab version strings as shell arithmetic via stored LTS aliases
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-121751?
CVE-2026-121751 is a low-severity vulnerability in nvm-sh nvm, published on 4 Nov 2026.
Official description
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.
Which versions are affected by CVE-2026-121751?
How do I fix CVE-2026-121751?
No fix has been published for CVE-2026-121751 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-121751 being exploited?
There is no known exploitation of CVE-2026-121751 in the wild and no public exploit code.
Sources
Also known as GHSA-7prg-rw9c-82h7.