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Vyper's nonpayable default functions are sometimes payable

Low severity GitHub Reviewed Published May 19, 2023 in vyperlang/vyper • Updated Nov 8, 2023

Package

pip vyper (pip)

Affected versions

< 0.3.8

Patched versions

0.3.8

Description

Impact

in contracts with at least one regular nonpayable function, due to the callvalue check being inside of the selector section, it is possible to send funds to the default function by using less than 4 bytes of calldata, even if the default function is marked nonpayable. this applies to contracts compiled with vyper<=0.3.7.

# @version 0.3.7

# implicitly nonpayable
@external
def foo() -> uint256:
    return 1

# implicitly nonpayable
@external
def __default__():
    # could receive ether here
    pass

Patches

this was fixed by the removal of the global calldatasize check in vyperlang/vyper@02339df.

Workarounds

don't use nonpayable default functions

References

@charles-cooper charles-cooper published to vyperlang/vyper May 19, 2023
Published by the National Vulnerability Database May 19, 2023
Published to the GitHub Advisory Database May 22, 2023
Reviewed May 22, 2023
Last updated Nov 8, 2023

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS score

0.065%
(30th percentile)

Weaknesses

CVE ID

CVE-2023-32675

GHSA ID

GHSA-vxmm-cwh2-q762

Source code

Credits

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