# CVE-2019-10744: lodash prototype pollution in defaultsDeep

Source: https://junglewise.ai/threats/cve-2019-10744-lodash-prototype-pollution-in-defaultsdeep  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2019-07-10. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2019-10744 · Severity: low · CVSS 3.1 · Published 2019-07-10

lodash is a widely-used JavaScript utility library for manipulating objects and arrays. A flaw in the defaultsDeep function allows attackers to inject properties into the JavaScript Object prototype, potentially corrupting or hijacking the behavior of all objects application-wide. This can lead to authentication bypasses, data tampering, or application crashes depending on how the affected code uses objects.

Technologies: [Lodash-Amd](https://junglewise.ai/threats/technologies/lodash-amd), [lodash (npm)](https://junglewise.ai/threats/technologies/lodash), [lodash-es (npm)](https://junglewise.ai/threats/technologies/lodash-es), [lodash.defaultsdeep (npm)](https://junglewise.ai/threats/technologies/lodash-defaultsdeep), [lodash-rails (RubyGems)](https://junglewise.ai/threats/technologies/lodash-rails). Vendors: [Lodash](https://junglewise.ai/threats/vendors/lodash), [npm](https://junglewise.ai/threats/vendors/npm), [RubyGems](https://junglewise.ai/threats/vendors/rubygems).

## Quick answers

**Is CVE-2019-10744 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2019-10744 being exploited in the wild.

**How severe is CVE-2019-10744?** Low severity, with a CVSS score of 3.1, published 10 July 2019.

**Which products and versions are affected?** Lodash-Amd before 4.17.13; lodash (npm) SEMVER:introduced=0,fixed=4.17.12; lodash-es (npm) SEMVER:introduced=0,fixed=4.17.14; lodash.defaultsdeep (npm) SEMVER:introduced=0,fixed=4.6.1; and 1 more.

**Is there a fix for CVE-2019-10744?** Yes. lodash (npm): upgrade to 4.17.12 or later; lodash-es (npm): upgrade to 4.17.14 or later; lodash.defaultsdeep (npm): upgrade to 4.6.1 or later; lodash-rails (RubyGems): upgrade to 4.17.12 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2019-10744 attacked?** It is attacked over the network.

**Am I affected by CVE-2019-10744?** Check whether you run Lodash-Amd, lodash (npm), lodash-es (npm) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- lodash (npm): upgrade to 4.17.12 or later

  ```sh
  npm install lodash@4.17.12
  ```

- lodash-es (npm): upgrade to 4.17.14 or later

  ```sh
  npm install lodash-es@4.17.14
  ```

- lodash.defaultsdeep (npm): upgrade to 4.6.1 or later

  ```sh
  npm install lodash.defaultsdeep@4.6.1
  ```

- lodash-rails (RubyGems): upgrade to 4.17.12 or later

  ```sh
  bundle update lodash-rails
  ```


## Technical details

The vulnerability is a prototype pollution flaw in lodash's defaultsDeep function (CWE-1321, CWE-20). Versions before 4.17.12 fail to properly validate input when merging nested objects, allowing a malicious user to inject properties via a crafted object with a {constructor: {prototype: {...}}} structure. The attack requires the application to call defaultsDeep with untrusted input (no authentication required, network-reachable if the function processes user-controlled data). An attacker can modify or add properties to Object.prototype, affecting all JavaScript objects in the application. The fix is available in lodash 4.17.12 (npm), 4.17.13 (lodash-amd), 4.17.14 (lodash-es), and 4.6.1 (lodash.defaultsdeep).

## Affected products

- lodash lodash before 4.17.12
- lodash lodash-es before 4.17.14
- lodash lodash-amd before 4.17.13
- lodash lodash.defaultsdeep before 4.6.1
- lodash lodash-rails before 4.17.12

## Identifiers

- CVE-2019-10744
- GHSA-jf85-cpcp-j695

## Timeline

- 2019-07-10: disclosed: Vulnerability published on 2019-07-10
- 2019-06-24: patched: Fix merged in lodash PR #4336 for 4.17.12-pre branch

## References

- [https://github.com/lodash/lodash/pull/4336](https://github.com/lodash/lodash/pull/4336)

## Related threats

- [lodash vulnerable to Code Injection via `_.template` imports key names](https://junglewise.ai/threats/cve-2021-23337-lodash-command-injection-in-template-function)
- [Lodash code injection in _.template imports](https://junglewise.ai/threats/cve-2026-4800-lodash-code-injection-in-template-imports)
- [Lodash prototype pollution in unset and omit functions](https://junglewise.ai/threats/cve-2026-2950-lodash-prototype-pollution-in-unset-and-omit-functions)
- [Lodash prototype pollution in _.unset and _.omit functions](https://junglewise.ai/threats/cve-2025-13465-lodash-prototype-pollution-in-unset-and-omit-functions)
- [lodash ReDoS in toNumber and trim functions](https://junglewise.ai/threats/cve-2020-28500-lodash-redos-in-tonumber-and-trim-functions)