# CVE-2026-4800 — lodash

> As of 2026-09-14, CVE-2026-4800 is a HIGH-severity vulnerability in lodash, CVSS v3.1 8.1, EPSS 2.6% (85.0th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-4800, most recently “CVE-2026-4800: Lodash `_.template` Arbitrary Code Injection — Broken 4.18.0 Patch Exposes Supply-Chain Patch-Pinning Risk”.

**Last updated:** 2026-09-14

## What is CVE-2026-4800?

Impact: The fix for CVE-2021-23337 (https://github.com/advisories/GHSA-35jh-r3h4-6jhm) added validation for the variable option in _.template but did not apply the same validation to options.imports key names. Both paths flow into the same Function() constructor sink. When an application passes untrusted input as options.imports key names, an attacker can inject default-parameter expressions that execute arbitrary code at template compilation time. Additionally, _.template uses assignInWith to merge imports, which enumerates inherited properties via for..in. If Object.prototype has been polluted by any other vector, the polluted keys are copied into the imports object and passed to Function(). Patches: Users should upgrade to version 4.18.0. Workarounds: Do not pass untrusted input as key names in options.imports. Only use developer-controlled, static key names.

The record classifies CVE-2026-4800 under weakness class [CWE-94](https://intel.threadlinqs.com/cwe/CWE-94). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 4 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 226 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 8.1 — HIGH (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **EPSS (FIRST):** 2.6% probability of exploitation in the next 30 days, higher than 85.0% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 9.5/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-03-31

## Is CVE-2026-4800 being exploited?

Weaponised exploit code for CVE-2026-4800 is publicly available. 2 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 34 in the Threadlinqs vulnerability feed.

- [threalwinky/CVE-2026-4800-POC](https://github.com/threalwinky/CVE-2026-4800-POC) (github)
- [SvenLie/next-rep-CVE-2026-4800](https://github.com/SvenLie/next-rep-CVE-2026-4800) (github)

## Affected products and versions

- **lodash**: lodash, lodash-es, lodash-amd, lodash.template

## How to fix CVE-2026-4800

No vendor patch reference has been recorded for CVE-2026-4800 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-4800

1 tracked threat in the Threadlinqs corpus references CVE-2026-4800, either in the campaign’s CVE list or as an indicator on the campaign record.

- [CVE-2026-4800: Lodash `_.template` Arbitrary Code Injection — Broken 4.18.0 Patch Exposes Supply-Chain Patch-Pinning Risk](https://intel.threadlinqs.com/threat/TL-2026-2151) — HIGH · 2026-08-26

## Sources

Enriched from CVE.org, FIRST EPSS, public proof-of-concept repositories.

**Other references**

- [github.com](https://github.com/advisories/GHSA-35jh-r3h4-6jhm)
- [github.com (3469357cff396a26c363f8c1b5a91dde28ba4b1c)](https://github.com/lodash/lodash/commit/3469357cff396a26c363f8c1b5a91dde28ba4b1c)
- [cna.openjsf.org](https://cna.openjsf.org/security-advisories.html)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-4800
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