Vulnerability in @npmcli/arborist (CVE-2021-39135)

Summary

Vulnerability in @npmcli/arborist (CVE-2021-39135). Confidential information can be exposed externally. Exploitable via node_modules. Mitigation: upgrade to 2.8.2 or later.

Original description

The description as published by the source.

Impact

Arbitrary File Creation, Arbitrary File Overwrite, Arbitrary Code Execution

@npmcli/arborist, the library that calculates dependency trees and manages the node_modules folder hierarchy for the npm command line interface, aims to guarantee that package dependency contracts will be met, and the extraction of package contents will always be performed into the expected folder.

This is accomplished by extracting package contents into a project's node_modules folder.

If the node_modules folder of the root project or any of its dependencies is somehow replaced with a symbolic link, it could allow Arborist to write package dependencies to any arbitrary location on the file system.

Note that symbolic links contained within package artifact contents are filtered out, so another means of creating a node_modules symbolic link would have to be employed.

A preinstall script could replace node_modules with a symlink. (This is prevented by using --ignore-scripts.)
An attacker could supply the target with a git repository, instructing them to run npm install --ignore-scripts in the root. This may be successful, because npm install --ignore-scripts is typically not capable of making changes outside of the project directory, so it may be deemed safe.

Patches

2.8.2 (included in npm v7.20.7 and above)

Workarounds

Do not run npm install on untrusted codebases, without first ensuring that the node_modules directory in the project is not a s…

Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2021-39135 has been found in @npmcli/arborist.
Attackers can target a specific entry point like node_modules over the network to misuse the product.
Confidential information can be exposed externally.
What to do: upgrade @npmcli/arborist to 2.8.2 or later.
If unsure, ask your IT team or search "@npmcli/arborist CVE-2021-39135" on the vendor's site.

CVE-2021-39135 (@npmcli/arborist) — CWE-59
Attack vector: local / unauthenticated
Attack surface: node_modules / preinstall / workspaces
Patched: 2.8.2 — apply immediately
Workaround: Do not run npm install on untrusted codebases, without first ensuring that the node_modules directory in the project is not a symbolic link.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-59) exists in @npmcli/arborist. Attackers reach the vulnerable code path via node_modules without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of @npmcli/arborist. Attack surface: node_modules / preinstall / workspaces.

🔥 Severity

Severity: ?. Confidential information can be exposed externally.

🔧 How to fix

Update to 2.8.2.

🛡️ Workaround

Workaround: Do not run npm install on untrusted codebases, without first ensuring that the node_modules directory in the project is not a symbolic link.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r '@npmcli/arborist' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r '@npmcli/arborist' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で @npmcli/arborist を grep し、稼働しているサービス・バージョンを把握する。
2
Apply temporary workaround mitigate
```
Do not run `npm install` on untrusted codebases, without first ensuring that the `node_modules` directory in the project is not a symbolic link.
```
パッチが適用されるまでの応急処置として、Do not run npm install on untrusted codebases, without first ensuring that the node_modules directory in the project is not a symbolic link. を実施。回避策の副作用 (機能低下) を確認した上で。
3
Apply patch patch
```
Upgrade @npmcli/arborist to 2.8.2
```
ステージング環境で 2.8.2 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
4
Post-deployment verification verify
```
Confirm patched version is live in production
```
パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

npm @npmcli/arborist

[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.8.2"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

Alpine Linux ALPINE-CVE-2021-39135 nodejs Fixed in: 12.22.6-r0
Debian DEBIAN-CVE-2021-39135 npm Fixed in: 7.24.0+ds-2