---
title: "CVE-2026-26021: set-in Affected by Prototype Pollution"
url: https://erroneo.us/security/cve/CVE-2026-26021/
description: "CVE-2026-26021 (set-in (npm)): set-in provides the set value of nested associative structure given array of keys. A prototype pollution vulnerability exists…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-02-11
date_modified: 2026-02-12
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-26021"
kev: false
cvss: 9.4
epss: 0.00562
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-26021: set-in Affected by Prototype Pollution

**Signal:** Critical, preconditions apply. Severe if exploited, but exploitation needs conditions that may not apply to you. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.6% , percentile 46: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 46% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.
- Only applies if your dependency tree includes set-in (npm) >= 2.0.1, < 2.0.5, fixed in 2.0.5 . Check your lockfile, including transitive dependencies.

## What it is

set-in provides the set value of nested associative structure given array of keys. A prototype pollution vulnerability exists in the the npm package set-in (>=2.0.1,

## Affected packages

- npm `set-in` >= 2.0.1, < 2.0.5 → fixed: 2.0.5

## Affected products (CVE record)

- ahdinosaur set-in: >= 2.0.1, < 2.0.5

## Severity

- GitHub_M CVSS 4.0: 9.4 `CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`
- GitHub CVSS 4.0: 9.4 `CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.56% probability of exploitation activity in the next 30 days; percentile 46.

## Sources

- [GitHub Advisory GHSA-2c4m-g7rx-63q7](https://github.com/advisories/GHSA-2c4m-g7rx-63q7)
- [CVE.org record CVE-2026-26021](https://www.cve.org/CVERecord?id=CVE-2026-26021)
- [NVD entry CVE-2026-26021](https://nvd.nist.gov/vuln/detail/CVE-2026-26021)
- [github.com](https://github.com/ahdinosaur/set-in/security/advisories/GHSA-2c4m-g7rx-63q7)
- [github.com](https://github.com/ahdinosaur/set-in/commit/b8e1dabfdbd35c8d604b6324e01d03f280256c3d)
- [github.com](https://github.com/ahdinosaur/set-in/pull/6)
- [github.com](https://github.com/ahdinosaur/set-in/commit/34842cc02de3fd65d6f8bd0b268347e7b390125b)
- [github.com](https://github.com/ahdinosaur/set-in/commit/6bad255961d379e4b1f5fbc52ef9dc8420816f24)
- [github.com](https://github.com/ahdinosaur/set-in/commit/d87c1a09fa2edb55cd76440a67d83d1cb828df11)

---
Source page: https://erroneo.us/security/cve/CVE-2026-26021/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt