Convict has prototype pollution via load(), loadFile(), and schema initialization

CVE-2026-33863 View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

Description

Impact

Two unguarded prototype pollution paths exist, not covered by previous fixes:

  1. config.load() / config.loadFile() — overlay() recursively merges config data without checking for forbidden keys. Input containing__proto__ or constructor.prototype (e.g. from a JSON file) causes the recursion to reach Object.prototype and write attacker-controlled values onto it.
  2. Schema initialization — passing a schema with constructor.prototype.* keys to convict({...}) causes default-value propagation to write directly to Object.prototype at startup.

Depending on how polluted properties are consumed, impact ranges from unexpected behavior to authentication bypass or RCE.

Workarounds

Do not pass untrusted data to load(), loadFile(), or convict().

Resources

Prior advisory: GHSA-44fc-8fm5-q62h
Related issue: https://github.com/mozilla/node-convict/issues/423

Basic information

Type
reviewed
Severity
critical
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2026-03-26 18:50:33 UTC
Updated
2026-03-26 18:50:36 UTC
GitHub reviewed
2026-03-26 18:50:33 UTC

EPSS Score

No EPSS score in this advisory JSON.

CVSS Scores

Base score Version Severity Vector
9.4 4.0 —
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 Click to expand
Attack vector (AV:L)
Attacker needs local access on the target system.
Attack complexity (AC:L)
Exploitation conditions are straightforward and stable.
Attack requirements (AT:N)
No additional preconditions are required beyond normal reachability.
Privileges required (PR:N)
No privileges are required.
User interaction (UI:N)
No user interaction is required.
Vulnerable system confidentiality impact (VC:H)
High confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:H)
High integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:H)
High availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:H)
High confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:H)
High integrity impact on subsequent systems.
Subsequent system availability impact (SA:H)
High availability impact on subsequent systems.

Identifiers

Type Value
GHSA GHSA-hf2r-9gf9-rwch ↗
CVE CVE-2026-33863 ↗

CWEs

CWE id Name
CWE-1321 Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Credits

  • toufali (finder)
  • clouserw (remediation_reviewer)

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
npm convict <= 6.2.4 6.2.5 —

References

cvelogic Threat Intelligence