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LodashApplication

CVE-2026-4800

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-31
Fix available
A fix is available. Upgrade to 4.18.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Lodash _.template has a code injection vulnerability where options.imports key names are not validated before being passed to the Function() constructor. Attackers can inject default-parameter expressions to achieve arbitrary code execution at template compilation time. Additionally, assignInWith's use of for..in enumeration allows Object.prototype pollution to be leveraged for exploitation.

MitigationUpgrade to Lodash version 4.18.0 or later. As a defensive measure, never pass untrusted input as key names in options.imports—only use developer-controlled, static key names.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
LodashApplication
Affected:>= 4.0.0, < 4.18.0
Lodash AmdApplication
Affected:>= 4.0.0, < 4.18.0
Lodash EsApplication
Affected:>= 4.0.0, < 4.18.0
Lodash.templateApplication
Affected:>= 4.0.0, < 4.18.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Lodash version
    Run `npm list lodash` or inspect your package.json dependencies to identify the exact version of Lodash installed
    Affected if The version is >= 4.0.0 and < 4.18.0
  2. Identify Lodash package variant
    Check which Lodash variant is in use (lodash, lodash-amd, lodash-es, or lodash.template) by examining your package.json import/require statements
    Affected if Any of these variants are present at version < 4.18.0
  3. Detect _.template usage with options.imports
    Search your codebase for usages of `_.template` or `template` that pass an options object containing an `imports` key, for example: `_.template(str, { imports: { ... } })`
    Affected if User-controlled or untrusted input is used as key names within the options.imports object
  4. Detect assignInWith usage
    Search your codebase for usages of `_.assignInWith` or `assignInWith` that merge user-controlled objects into a target object
    Affected if Untrusted or user-controlled objects are passed as sources to assignInWith, which could enable Object.prototype pollution

You are affected if your installed Lodash version is >= 4.0.0 and < 4.18.0 AND you use _.template with untrusted options.imports key names OR assignInWith with untrusted source objects.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.18.0 or later
Fixed in 4.18.0
Vendor patch github.com →
Interim mitigation

Upgrade to Lodash version 4.18.0 or later. As a defensive measure, never pass untrusted input as key names in options.imports—only use developer-controlled, static key names.

Recommended fix High confidence

[email protected] (and lodash-amd, lodash-es, lodash.template at version 4.18.0)

  1. Identify all project dependencies that include lodash (e.g., lodash, lodash-amd, lodash-es, lodash.template) using npm ls lodash or equivalent package manager command
  2. Update lodash to version 4.18.0 by running: npm install [email protected] (or yarn add [email protected] / pnpm add [email protected])
  3. If using bundler-level lodash imports (e.g., lodash-amd, lodash-es), update those packages similarly to their 4.18.0 versions
  4. Re-run application tests to verify template functionality works as expected
  5. If your application uses options.imports in _.template, audit the code to ensure key names are developer-controlled static values rather than user-supplied input
  6. Rebuild and deploy the updated application
Caveat Lodash 4.18.0 is a minor version within the 4.x line; breaking changes are unlikely but review release notes for any template-related changes

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Lodash Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing8.0 h
  • Review / QA4.0 h
18.0 hours of engineering $3,080
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-4800 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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