CVE-2024-27094 — @openzeppelin/contracts
MEDIUMFix: OpenZeppelin/openzeppelin-contracts-upgradeable@2d081f2CVE-2024-27094 is a medium-severity (CVSS 6.5) Out-of-bounds Read vulnerability in @openzeppelin/contracts. A fix is available for @openzeppelin/contracts — see the affected versions and patch details below.
OpenZeppelin Contracts base64 encoding may read from potentially dirty memory
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-27094.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2024-27094 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@openzeppelin/contractsnpm@openzeppelin/contracts-upgradeablenpmDescription
Impact
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.
Although the encode function pads the output for these cases, up to 4 bits of data are kept between the encoding and padding, corrupting the output if these bits were dirty (i.e. memory after the input is not 0). These conditions are more frequent in the following scenarios:
- A
bytes memorystruct is allocated just after the input and the first bytes of it are non-zero. - The memory pointer is set to a non-empty memory location before allocating the input.
Developers should evaluate whether the extra bits can be maliciously manipulated by an attacker.
Patches
Upgrade to 5.0.2 or 4.9.6.
References
This issue was reported by the Independent Security Researcher Riley Holterhus through Immunefi (@rileyholterhus on X)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @openzeppelin/contracts | ≥ 4.5.0&&< 4.9.6 | 4.9.6npm install @openzeppelin/contracts@4.9.6 |
| 📦npm | @openzeppelin/contracts-upgradeable | ≥ 5.0.0-rc.0&&< 5.0.2 | 5.0.2npm install @openzeppelin/contracts-upgradeable@5.0.2 |
| 📦npm | @openzeppelin/contracts | ≥ 5.0.0-rc.0&&< 5.0.2 | 5.0.2npm install @openzeppelin/contracts@5.0.2 |
| 📦npm | @openzeppelin/contracts-upgradeable | ≥ 4.5.0&&< 4.9.6 | 4.9.6npm install @openzeppelin/contracts-upgradeable@4.9.6 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @openzeppelin/contracts, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @openzeppelin/contracts to 4.9.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-27094 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2024-27094 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2024-27094. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2024-27094 in your dependencies?
O3 Security finds CVE-2024-27094 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.