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Not in CISA KEV
MEDIUM severity

CVE-2021-23771 — notevil

MEDIUM

CVE-2021-23771 is a medium-severity (CVSS 6.5) CWE-1321 vulnerability in notevil. 2 public exploit or proof-of-concept references are indexed, so weaponization risk is real. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

Sandbox escape in notevil and argencoders-notevil

Published
Updated
Affected
2 pkgs
Patched
See advisory
Exploits
2 known
Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.0%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs63th percentile — riskier than 63% of all scored CVEsHighest risk
0.00%0.50%1.01%1.51%0.3%1.0%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.

notevilnpm
56Kdownloads / week
argencoders-notevilnpm
33downloads / week

Description

This affects all versions of package notevil; all versions of package argencoders-notevil. It is vulnerable to Sandbox Escape leading to Prototype pollution. The package fails to restrict access to the main context, allowing an attacker to add or modify an object's prototype. Note: This vulnerability derives from an incomplete fix in SNYK-JS-NOTEVIL-608878. This package has been deprecated.

Affected Packages

2 total
EcosystemPackageVulnerable rangeFix
📦npmnotevilall versionsNo fix
📦npmargencoders-notevilall versionsNo fix

Affected Products

2 products · 2 configurations
Application
argencoders-notevilargencoders-notevil_project
≤ 2.5.0
range
Application
notevilnotevil_project
≤ 1.3.3
range
Exploits & PoCs
2

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

This affects all versions of package notevil; all versions of package ar…

snyk.ioNVDMar 2022

Report on snyk.io

snyk.ioNVDMar 2022

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for notevil, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    The records we use list no patched version of notevil for CVE-2021-23771. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

  3. Mitigate without a patch

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

This affects all versions of package notevil; all versions of package argencoders-notevil. It is vulnerable to Sandbox Escape leading to Prototype pollution. The package fails to restrict access to the main context, allowing an attacker to add or modify an object's prototype. **Note:** This vulnerability derives from an incomplete fix in [SNYK-JS-NOTEVIL-608878](https://security.snyk.io/vuln/SNYK-JS-NOTEVIL-608878). This package has been deprecated.
O3 Security · Impact-Aware SCA

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CVE-2021-23771: notevil (Medium 6.5)