CVE-2021-39168Network attack vector

Timelock takeover via delay reset

Published Aug 26, 2021 · Updated Aug 4, 2024

Improper privilege management in OpenZeppelin Contracts Upgradeable 3.3.0 through 4.3.0 allows remote attackers to seize TimelockController control via executor access. TimelockController lets an executor reset the timelock delay to zero, then escalate roles and execute unrestricted operations against assets held by the contract. Exploitation requires executor authority; deployments with an open executor role allow anyone able to submit transactions to take over the timelock, causing loss of control, asset theft, or governance disruption.

CVSS severity9.8
Critical
EPSS probability1.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper privilege management in OpenZeppelin Contracts Upgradeable 3.3.0 through 4.3.0 allows remote attackers to seize TimelockController control via executor access. TimelockController lets an executor reset the timelock delay to zero, then escalate roles and execute unrestricted operations against assets held by the contract. Exploitation requires executor authority; deployments with an open executor role allow anyone able to submit transactions to take over the timelock, causing loss of control, asset theft, or governance disruption.

The record

CVE
CVE-2021-39168
Published
Aug 26, 2021
Updated
Aug 4, 2024
Vendor
OpenZeppelin
Product
OpenZeppelin Contracts Upgradeable
Classifications
CWE-269, T1548
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>=3.3.0, < 3.4.2
  2. Affected versionversion=>= 3.3.0-solc-0.7, < 3.4.2-solc-0.7
  3. Affected versionversion=>=4.0.0, < 4.3.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

OpenZeppelin · OpenZeppelin Contracts Upgradeableversion=>=3.3.0, < 3.4.2; version=>= 3.3.0-solc-0.7, < 3.4.2-solc-0.7; version=>=4.0.0, < 4.3.1

Published CVSS scores

10.0GitHub CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-269Improper Privilege Management
T1548Abuse Elevation Control Mechanism

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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