CVE-2023-32058

Vyper vulnerable to integer overflow in loop

Workarounds

Due to missing overflow check for loop variables, by assigning the iterator of a loop to a variable, it is possible to overflow the type of the latter.

In the following example, calling test returns 354, meaning that the variable a did store 354 a value out of bound for the type uint8.

@external
def test() -> uint16:
    x:uint8 = 255
    a:uint8 = 0
    for i in range(x, x+100):
        a = i
    return convert(a,uint16)

The issue seems to happen only in loops of type for i in range(a, a + N) as in loops of type for i in range(start, stop) and for i in range(stop), the compiler is able to raise a TypeMismatch when trying to overflow the variable.

thanks to @trocher for reporting

An arithmetic operation produces a value that exceeds the integer type's maximum, causing it to wrap to an unexpected small value. Typical impact: incorrect size calculations leading to heap overflows or logic errors.

CVE-2023-32058 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.3.8); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

patched in 3de1415ee77a9244eb04bdb695e249d3ec9ed868

1. What is CVE-2023-32058? CVE-2023-32058 is a high-severity integer overflow or wraparound vulnerability in vyper (pip), affecting versions < 0.3.8. It is fixed in 0.3.8. An arithmetic operation produces a value that exceeds the integer type's maximum, causing it to wrap to an unexpected small value.
2. How severe is CVE-2023-32058? CVE-2023-32058 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of vyper are affected by CVE-2023-32058? vyper (pip) versions < 0.3.8 is affected.
4. Is there a fix for CVE-2023-32058? Yes. CVE-2023-32058 is fixed in 0.3.8. Upgrade to this version or later.
5. Is CVE-2023-32058 exploitable, and should I be worried? Whether CVE-2023-32058 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-32058 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-32058? Upgrade vyper to 0.3.8 or later.

Other vulnerabilities in vyper