CVE-2025-27105
Published: 21 February 2025
Description
vyper is a Pythonic Smart Contract Language for the EVM. Vyper handles AugAssign statements by first caching the target location to avoid double evaluation. However, in the case when target is an access to a DynArray and the rhs modifies the array, the cached target will evaluate first, and the bounds check will not be re-evaluated during the write portion of the statement. This issue has been addressed in version 0.4.1 and all users are advised to upgrade. There are no known workarounds for this vulnerability.
Security Summary
CVE-2025-27105 is a vulnerability in Vyper, a Pythonic smart contract language for the Ethereum Virtual Machine (EVM). The flaw occurs in the handling of AugAssign statements, where Vyper caches the target location for dynamic array (DynArray) accesses to avoid double evaluation. However, if the right-hand side (rhs) of the statement modifies the array, the bounds check is not re-evaluated during the write operation, enabling an out-of-bounds write (CWE-787). This affects Vyper versions prior to 0.4.1.
The vulnerability carries a CVSS v3.1 base score of 9.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H), making it remotely exploitable with low attack complexity, no privileges, and no user interaction required. Attackers can target smart contracts compiled with vulnerable Vyper versions, achieving high integrity and availability impacts through arbitrary memory writes, such as corrupting contract state or causing denial of service.
The issue has been fixed in Vyper version 0.4.1, and all users are advised to upgrade immediately. No workarounds are available. Additional details are provided in the GitHub Security Advisory at https://github.com/vyperlang/vyper/security/advisories/GHSA-4w26-8p97-f4jp.
Details
- CWE(s)