# CVE-2026-15921: nvm path traversal via a malicious mirror's LTS codename writes outside the alias directory

> A malicious mirror can exploit path traversal in nvm to overwrite shell startup files, leading to code execution when the user opens a new terminal.

- **Severity:** Low 2.1 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 15 Jul 2026
- **Updated:** 16 Jul 2026
- **Also known as:** GHSA-4ghp-wxpw-rhpg

## What is CVE-2026-15921?

CVE-2026-15921 is a low-severity path traversal vulnerability in nvm-sh nvm, published on 15 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Node Version Manager (nvm) is a POSIX-compliant shell function for managing multiple node.js versions. In versions 0.32.1 through 0.40.5, `nvm ls-remote` (and other commands that refresh remote LTS aliases, such as `nvm install --lts`) parse the node.js mirror's `index.tab` and use each release's LTS codename field as an alias filename without validating it. A malicious, compromised, or man-in-the-middled mirror can return an LTS codename containing path-traversal sequences such as `../../../.bashrc`, causing nvm to write the associated version string to a path outside `$NVM_DIR/alias`. With the default layout (`$NVM_DIR` is `~/.nvm`), this can create or overwrite files in the user's home directory, including shell startup files, which can lead to code execution in a later shell session. Exploitation requires the victim to use a hostile mirror -- via a compromised mirror or CDN, a network man-in-the-middle, or a maliciously configured `NVM_NODEJS_ORG_MIRROR`/`NVM_IOJS_ORG_MIRROR` -- and to run an affected command. Version 0.40.6 validates remote LTS codenames as safe alias filenames and rejects `..` path components when writing alias files.

Weakness: CWE-73 (External Control of File Name or Path), CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-15921?


## How do I fix CVE-2026-15921?

No fix has been published for CVE-2026-15921 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-15921 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-15921 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-15921 and fix it if it is affected.

What it is: CVE-2026-15921 is a low-severity path traversal vulnerability in nvm-sh nvm, published on 15 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-15921 exists.

Affected product: nvm-sh nvm. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-15921/ (Markdown: https://insights.sbomify.com/CVE-2026-15921/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-15921
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-15921
- OSV: https://osv.dev/vulnerability/CVE-2026-15921

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-15921/
Summaries are generated and may contain mistakes; the official description above is the record.