nvm evaluates a malicious mirror's index.tab version strings as shell arithmetic via stored LTS aliases
Summary
| CVE | CVE-2026-121751 |
|---|---|
| State | PUBLISHED |
| Assigner | harborist |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-11-04 22:17:55 UTC |
| Updated | 2026-11-04 22:17:55 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 2.1 LOW from 7ffcee3d-2c14-4c3e-b844-86c6a321a158
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Problem Types: CWE-20 | CWE-78 | CWE-78 CWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') | CWE-20 CWE-20 Improper Input Validation
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 7ffcee3d-2c14-4c3e-b844-86c6a321a158 | Secondary | 2.1 | LOW | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/C... |
| 4.0 | CNA | CVSS | 2.1 | LOW | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N |
| 3.1 | 7ffcee3d-2c14-4c3e-b844-86c6a321a158 | Secondary | 3.1 | LOW | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N |
| 3.1 | CNA | CVSS | 3.1 | LOW | CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N |
CVSS v4.0 Breakdown
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/nvm-sh/nvm/security/advisories/GHSA-7prg-rw9c-82h7 | 7ffcee3d-2c14-4c3e-b844-86c6a321a158 | github.com | |
| github.com/nvm-sh/nvm/commit/aa0572b7c48b2652a9f86276bbbf3840939981af | 7ffcee3d-2c14-4c3e-b844-86c6a321a158 | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Anthropic's OSS Scanner, as vulnerabilities ANT-2026-0GXXE91V and ANT-2026-31ZIEY85 (en)
CNA: Adel Assakaf (https://github.com/assakafpix) (en)
CNA: Jordan Harband (https://github.com/ljharb) (en)
Additional Advisory Data
Solutions
CNA: 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
CNA: 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.