OpenZeppelin Contracts initializer reentrancy may lead to double initialization

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2021-46320: 1.22% estimated exploitation activity in the next 30 days; percentile 68.64 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
• CVE-2022-39384: 0.66% estimated exploitation activity in the next 30 days; percentile 51.67 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Initializer functions that are invoked separate from contract creation (the most prominent example being minimal proxies) may be reentered if they make an untrusted non-view external call. Once an initializer has finished running it can never be re-executed. However, an exception put in place to support multiple inheritance made reentrancy possible in the scenario described above, breaking the expectation that there is a single execution. Note that upgradeable proxies are commonly initialized together with contract creation, where reentrancy is not feasible, so the impact of this issue is believed to be minor.

Patches A fix is included in the version v4.4.1 of `@openzeppelin/contracts` and `@openzeppelin/contracts-upgradeable`.

Workarounds Avoid untrusted external calls during initialization.

References https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3006

Credits This issue was identified and reported by @chaitinblockchain through our bug…

Published by the source

5 Feb 2022, 00:00 UTC

Last modified by the source

16 Jul 2026, 03:59 UTC

Source last checked

24 Oct 2026, 04:13 UTC

1. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-9c22-pwxw-p6hx

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-88g8-f5mf-f5rj

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2021-46320

Advisory: OpenZeppelin Contracts initializer reentrancy may lead to double initialization
IDs: CVE-2021-46320, GHSA-88g8-f5mf-f5rj
Record: https://patchnext.com/advisories/cve-2021-46320 (revision 2, source checked 24 Oct 2026, 04:13 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @openzeppelin/contracts 4.4.1; @openzeppelin/contracts-upgradeable 4.4.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @openzeppelin/contracts: affected >= 3.2.0, < 4.4.1; fixed in 4.4.1
- npm @openzeppelin/contracts-upgradeable: affected >= 3.2.0, < 4.4.1; fixed in 4.4.1

## Suggested inspection (read-only)
- `npm ls @openzeppelin/contracts --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @openzeppelin/contracts-upgradeable --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @openzeppelin/contracts, @openzeppelin/contracts-upgradeable.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-88g8-f5mf-f5rj (OSV record GHSA-88g8-f5mf-f5rj lists affected ranges: npm @openzeppelin/contracts >=0 <4.4.1 (fixed))
- Verified: https://osv.dev/vulnerability/GHSA-9c22-pwxw-p6hx (OSV record GHSA-9c22-pwxw-p6hx lists affected ranges: npm @openzeppelin/contracts >=3.2.0 =3.2.0 <4.4.1 (fixed))

Commands are suggestions: review each one before running it.