# CVE-2026-33863: Convict prototype pollution in load and loadFile

Source: https://junglewise.ai/threats/cve-2026-33863-convict-prototype-pollution-in-load-and-loadfile  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-26. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-33863 · Severity: medium · CVSS 4 · Published 2026-03-26

Convict is a Node.js configuration management library used by applications to load and validate application settings. A prototype pollution vulnerability allows attackers to inject malicious properties into JavaScript's Object.prototype through untrusted configuration data, potentially leading to authentication bypass, application crashes, or remote code execution depending on how the polluted properties are used.

Technologies: [convict (npm)](https://junglewise.ai/threats/technologies/convict). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-33863 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-33863 being exploited in the wild.

**How severe is CVE-2026-33863?** Medium severity, with a CVSS score of 4, published 26 March 2026.

**Which products and versions are affected?** convict (npm) SEMVER:introduced=0,fixed=6.2.5.

**Is there a fix for CVE-2026-33863?** Yes. convict (npm): upgrade to 6.2.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-33863 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-33863?** Check whether you run convict (npm) 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

- convict (npm): upgrade to 6.2.5 or later

  ```sh
  npm install convict@6.2.5
  ```


## Technical details

The vulnerability is a prototype pollution flaw (CWE-1321) in Convict's overlay() function and schema initialization logic. The overlay() method recursively merges configuration data without validating forbidden keys like __proto__ or constructor.prototype; untrusted input (e.g., from JSON files via load() or loadFile()) can reach Object.prototype and write attacker-controlled values. Similarly, passing a schema with constructor.prototype.* keys to convict() causes default-value propagation to pollute Object.prototype at startup. The attack requires no authentication or user interaction—only that the application passes untrusted data to load(), loadFile(), or the constructor. Impact ranges from unexpected behavior to authentication bypass or RCE if polluted properties are consumed by dangerous sinks. The vulnerability is fixed in version 6.2.5.

## Affected products

- Mozilla Convict <= 6.2.4

## Identifiers

- CVE-2026-33863
- GHSA-hf2r-9gf9-rwch

## Timeline

- 2026-03-26: disclosed: Advisory GHSA-hf2r-9gf9-rwch published

## References

- [https://github.com/mozilla/node-convict/security/advisories/GHSA-44fc-8fm5-q62h](https://github.com/mozilla/node-convict/security/advisories/GHSA-44fc-8fm5-q62h)
- [https://github.com/mozilla/node-convict/security/advisories/GHSA-hf2r-9gf9-rwch](https://github.com/mozilla/node-convict/security/advisories/GHSA-hf2r-9gf9-rwch)

## Related threats

- [Convict prototype pollution via startsWith bypass](https://junglewise.ai/threats/cve-2026-33864-convict-prototype-pollution-via-startswith-bypass)
- [convict prototype pollution](https://junglewise.ai/threats/cve-2023-0163-convict-prototype-pollution)
- [convict prototype pollution vulnerability](https://junglewise.ai/threats/cve-2022-21190-convict-prototype-pollution-vulnerability)
- [Mozilla Convict prototype pollution in configuration handling](https://junglewise.ai/threats/cve-2022-22143-mozilla-convict-prototype-pollution-in-configuration-handling)