CVE-2018-18920
CVE-2018-18920 is a high-severity vulnerability in Ethereum Py-evm with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-119.
Key facts
- Severity: High (CVSS 3.x base score 8.8)
- CVSS v2: 6.8
- EPSS exploit prediction: 3% (87th percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-119
- Affected product: Ethereum Py-evm
- Published:
- Last modified:
Description
Py-EVM v0.2.0-alpha.33 allows attackers to make a vm.execute_bytecode call that triggers computation._stack.values with '"stack": [100, 100, 0]' where b'\x' was expected, resulting in an execution failure because of an invalid opcode. This is reportedly related to "smart contracts can be executed indefinitely without gas being paid."
Frequently asked questions
- What is CVE-2018-18920?
- Py-EVM v0.2.0-alpha.33 allows attackers to make a vm.execute_bytecode call that triggers computation._stack.values with '"stack": [100, 100, 0]' where b'\x' was expected, resulting in an execution failure because of an invalid opcode. This is reportedly related to "smart contracts can be executed indefinitely without gas being paid."
- How severe is CVE-2018-18920?
- CVE-2018-18920 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2018-18920 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (87th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2018-18920?
- CVE-2018-18920 affects Ethereum Py-evm. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2018-18920?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- When was CVE-2018-18920 published?
- CVE-2018-18920 was published on 2018-11-12 and last updated on 2026-06-17.
References
- https://github.com/ethereum/py-evm/issues/1448
- https://twitter.com/AlexanderFisher/status/1060923428641878019
- https://twitter.com/NettaLab/status/1060889400102383617
- https://www.reddit.com/r/ethereum/comments/9vkk2g/netta_labs_claim_to_have_found_a_vulnerability_in/e9d3wyx/
Affected products (1)
- cpe:2.3:a:ethereum:py-evm:0.2.0:alpha.33:*:*:*:*:*:*
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