Summary
OpenZeppelin Contracts contains Improper Verification of Cryptographic Signature
Cause
is_valid_eth_signature is missing a call to finalize_keccak after calling verify_eth_signature.
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.
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]
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.
CVE-2023-23940 has a CVSS score of 5.3 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.6.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The issue has been patched in 0.6.1.
Frequently Asked Questions
- What is CVE-2023-23940? CVE-2023-23940 is a medium-severity security vulnerability in openzeppelin-cairo-contracts (pip), affecting versions >= 0.2.0, < 0.6.1. It is fixed in 0.6.1.
- How severe is CVE-2023-23940? CVE-2023-23940 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of openzeppelin-cairo-contracts are affected by CVE-2023-23940? openzeppelin-cairo-contracts (pip) versions >= 0.2.0, < 0.6.1 is affected.
- Is there a fix for CVE-2023-23940? Yes. CVE-2023-23940 is fixed in 0.6.1. Upgrade to this version or later.
- Is CVE-2023-23940 exploitable, and should I be worried? Whether CVE-2023-23940 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-23940 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-23940? Upgrade
openzeppelin-cairo-contractsto 0.6.1 or later.