CVE-2024-32481mediumCWE-681

CVE-2024-32481: medium-severity vulnerability in vyperlang vyper

vyper's range(start, start + N) reverts for negative numbers

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13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 5.3epss 0.8%
In short

Vyper smart contracts using range loops with negative starting values will fail unexpectedly. This is a bug in how Vyper generates code for these loops, making them unusable when the start value is negative.

Technical detail

CWE-681 involves incorrect numeric comparison in Vyper's range() code generation for signed integers. When start is negative in range(start, start + N), the compiler incorrectly uses an unsigned comparison (le) instead of signed comparison (sle), causing the negative value to be interpreted as a large unsigned integer and the assertion to always fail, resulting in transaction revert.

Summary generated and translated by AI from the official description.
Vyper is a pythonic Smart Contract Language for the Ethereum virtual machine. Starting in version 0.3.8 and prior to version 0.4.0b1, when looping over a `range` of the form `range(start, start + N)`, if `start` is negative, the execution will always revert. This issue is caused by an incorrect assertion inserted by the code generation of the range `stmt.parse_For_range()`. The issue arises when `start` is signed, instead of using `sle`, `le` is used and `start` is interpreted as an unsigned integer for the comparison. If it is a negative number, its 255th bit is set to `1` and is hence interpreted as a very large unsigned integer making the assertion always fail. Any contract having a `range(start, start + N)` where `start` is a signed integer with the possibility for `start` to be negative is affected. If a call goes through the loop while supplying a negative `start` the execution will revert. Version 0.4.0b1 fixes the issue.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Affected products
vyperlang · vyper
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