CVE-2025-21607: 
Python vulnerability analysis and mitigation

CVE-2025-21607 affects Vyper, a Pythonic Smart Contract Language for the Ethereum Virtual Machine (EVM). The vulnerability was discovered and disclosed on January 14, 2025, and involves the Vyper Compiler's handling of precompiles EcRecover (0x1) and Identity (0x4). The core issue lies in the compiler's failure to check the success flag of these precompile calls (GitHub Advisory).

The vulnerability stems from the Vyper Compiler's implementation of precompile calls where the success flag is not verified for EcRecover (0x1) and Identity (0x4) operations. According to the EVM's rules, after a failed precompile call, the remaining code has only 1/64 of the pre-call-gas left, as 63/64 were forwarded and spent. The vulnerability has been assigned a CVSS v4.0 score of 2.3 (LOW) with the vector string CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N (NVD).

An attacker can exploit this vulnerability by providing a specific amount of gas to make these precompile calls fail while allowing the overall execution to continue. This results in incorrect execution results, though the impact is limited due to the gas constraints that restrict the complexity of operations that can follow the failed precompile calls. No significantly impacted real-world contracts have been identified (GitHub Advisory).

Currently, there are no direct actions required from users as the impact on real-world contracts has been assessed as minimal. The issue is being tracked for resolution, and users are advised to monitor for updates from the Vyper team (GitHub Advisory).