CVE-2025-27105 — Out-of-bounds Write in Vyperlang Vyper

Vendor	Product	Version range	Fixed in
vyperlang	vyper	< 0.4.1	0.4.1
vyperlang	vyper	>= 0 < 0.4.1	0.4.1

OSV

CVE-2025-27105: vyper is a Pythonic Smart Contract Language for the EVM

osv·2025-02-21

CVE-2025-27105 CVE-2025-27105: vyper is a Pythonic Smart Contract Language for the EVM 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.

OSV

AugAssign evaluation order causing OOB write within the object in Vyper

osv·2025-02-21

CVE-2025-27105 [LOW] AugAssign evaluation order causing OOB write within the object in Vyper AugAssign evaluation order causing OOB write within the object in Vyper 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. In other words, the following code ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] a[1] += a.pop() ``` is equivalent to: ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] a[1] += a[len(a) - 1] a.pop() ``` rather than: ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] s: uint256 = a[1] t: uint256 = a.pop() a[1] = s + t # reverts due to oob access ```

GHSA

AugAssign evaluation order causing OOB write within the object in Vyper

ghsa·2025-02-21

CVE-2025-27105 [LOW] CWE-787 AugAssign evaluation order causing OOB write within the object in Vyper AugAssign evaluation order causing OOB write within the object in Vyper 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. In other words, the following code ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] a[1] += a.pop() ``` is equivalent to: ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] a[1] += a[len(a) - 1] a.pop() ``` rather than: ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] s: uint256 = a[1] t: uint256 = a.pop() a[1] = s + t # reverts due to oob access ```

CVE-2025-27105: vyper is a Pythonic Smart Contract Language for the EVM. Vyper handles AugAssign statements by first caching the target location to avoid double evaluation…

Affected

CVSS provenance