CVE-2023-23940 is a medium-severity (CVSS 6.4) CWE-345 vulnerability in openzeppelin-cairo-contracts. A fix is available for openzeppelin-cairo-contracts — see the affected versions and patch details below.
OpenZeppelin Contracts for Cairo is vulnerable to signature validation bypass
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-2023-23940.
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-2023-23940 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 377,636 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
openzeppelin-cairo-contractsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Cause
is_valid_eth_signature is missing a call to finalize_keccak after calling verify_eth_signature.
Impact
As a result, any contract using is_valid_eth_signature from the account library (such as the EthAccount preset) is vulnerable to a malicious sequencer. Specifically, the malicious sequencer would be able to bypass signature validation to impersonate an instance of these accounts.
Risk
In order to exploit this vulnerability, it is required to control a sequencer or prover since they're the ones executing the hints, being able to inject incorrect keccak results.
Today StarkWare is the only party running both a prover or a sequencer, greatly reducing the risk of exploit.
Patches
The issue has been patched in 0.6.1.
For more information
If you have any questions or comments about this advisory:
- Open an issue in the Contracts for Cairo repository
- Email us at [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | openzeppelin-cairo-contracts | ≥ 0.2.0&&< 0.6.1 | 0.6.1pip install --upgrade 'openzeppelin-cairo-contracts==0.6.1' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for openzeppelin-cairo-contracts, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update openzeppelin-cairo-contracts to 0.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-23940 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-2023-23940 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-23940. 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-2023-23940 in your dependencies?
O3 Security finds CVE-2023-23940 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.