CVE-2025-21607: Success of Certain Precompile Calls not Checked in Vyper

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2025-01-14 · updated 2026-06-17
Weakness: CWE-670

Description

Vyper is a Pythonic Smart Contract Language for the EVM. When the Vyper Compiler uses the precompiles EcRecover (0x1) and Identity (0x4), the success flag of the call is not checked. As a consequence an attacker can provide a specific amount of gas to make these calls fail but let the overall execution continue. Then the execution result can be incorrect. Based on EVM's rules, after the failed precompile the remaining code has only 1/64 of the pre-call-gas left (as 63/64 were forwarded and spent). Hence, only fairly simple executions can follow the failed precompile calls. Therefore, we found no significantly impacted real-world contracts. None the less an advisory has been made out of an abundance of caution. This issue is fixed in 0.4.1.

Affected products

vyperlang vyper: before 0.4.1 — fixed in 0.4.1

How to fix

Upgrade to a fixed version: vyperlang vyper 0.4.1. Check the vendor advisory for mitigations.

References

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