CVE-2024-27094: OpenZeppelin Contracts is a library for secure smart contract development

Q: How do I fix CVE-2024-27094?

contracts: upgrade to 4.9.6, 5.0.2; contracts upgradeable: upgrade to 5.0.2. Exact commands for each OS are on this page.

Q: Is CVE-2024-27094 being exploited?

CVE-2024-27094 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2024-27094 affect?

CVE-2024-27094 affects contracts, contracts upgradeable. Severity is medium (CVSS 6.5). OpenZeppelin Contracts is a library for secure smart contract development. The `Base64.encode` function encodes a `bytes` input by iterating over it in chunks of 3 bytes. When this input is not a multiple of 3, the last iteration may read p

Q: How urgent is CVE-2024-27094?

Priority 42/100. Remotely exploitable, no login, no user action

This month

MEDIUM 6.5REMOTEUPGRADEUPGRADE

CVE-2024-27094 is a medium-severity flaw (CVSS 6.5) affecting contracts, contracts upgradeable. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

OpenZeppelin Contracts is a library for secure smart contract development. The `Base64.encode` function encodes a `bytes` input by iterating over it in chunks of 3 bytes. When this input is not a multiple of 3, the last iteration may read parts of the memory that are beyond the input buffer. The vulnerability is fixed in 5.0.2 and 4.9.6.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.8% (top 45%)
CISA exploited list	No
Weakness	CWE-125
Published	2024-03-21
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: openzeppelin

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2024-03-21 02:52 UTCPublished CVE record published
2026-06-17 07:19 UTCUpdated Record last modified

openzeppelin contracts UPGRADE

Affected: >= 4.5.0 and < 4.9.6 · >= 5.0.0 and < 5.0.2

Fixed in: 4.9.6, 5.0.2

Safe to downgrade to: a release before 4.5.0

1. Check installed version

npm ls contracts

2. UPGRADE to 4.9.6

npm install contracts@">=4.9.6"

3. If no update is available yet, DOWNGRADE to a release before 4.5.0

npm view contracts versions npm install contracts@"<4.5.0"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

openzeppelin contracts upgradeable UPGRADE

Affected: >= 4.5.0 and <= 4.9.6 · >= 5.0.0 and < 5.0.2

Fixed in: 5.0.2

Safe to downgrade to: a release before 4.5.0

1. Check installed version

npm ls contracts-upgradeable

2. UPGRADE to 5.0.2

npm install contracts-upgradeable@">=5.0.2"

3. If no update is available yet, DOWNGRADE to a release before 4.5.0

npm view contracts-upgradeable versions npm install contracts-upgradeable@"<4.5.0"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2024-27094?

contracts: upgrade to 4.9.6, 5.0.2; contracts upgradeable: upgrade to 5.0.2. Exact commands for each OS are on this page.

Is CVE-2024-27094 being exploited?

CVE-2024-27094 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2024-27094 affect?

CVE-2024-27094 affects contracts, contracts upgradeable. Severity is medium (CVSS 6.5). OpenZeppelin Contracts is a library for secure smart contract development. The `Base64.encode` function encodes a `bytes` input by iterating over it in chunks of 3 bytes. When this input is not a multiple of 3, the last iteration may read p

How urgent is CVE-2024-27094?

Priority 42/100. Remotely exploitable, no login, no user action

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CVE-2023-49798 MEDIUM 5.9 DOWNGRADE DOWNGRADE OpenZeppelin Contracts is a library for smart contract development
CVE-2023-34459 MEDIUM 5.3 UPGRADE UPGRADE OpenZeppelin Contracts is a library for smart contract development
CVE-2023-34234 MEDIUM 5.3 UPGRADE UPGRADE OpenZeppelin Contracts is a library for smart contract development

References

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