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vyper default functions don't respect nonreentrancy keys

Moderate severity GitHub Reviewed Published Apr 25, 2024 in vyperlang/vyper • Updated Apr 25, 2024

Package

pip vyper (pip)

Affected versions

<= 0.2.16

Patched versions

0.3.0

Description

Summary

Prior to v0.3.0, __default__() functions did not respect the @nonreentrancy decorator and the lock was not emitted. This is a known bug and was already visible in the issue tracker (vyperlang/vyper#2455), but it is being re-issued as an advisory so that tools relying on the advisory publication list can incorporate it into their searches.

A contract search was additionally performed and no vulnerable contracts were found in production.

PoC

@external
@payable
@nonreentrant("default")
def __default__():
    pass

after codegen:

[seq,
  [if, [lt, calldatasize, 4], [goto, fallback]],
  [mstore, 28, [calldataload, 0]],
  [with, _func_sig, [mload, 0], seq],
  [seq_unchecked,
    [label, fallback],
    [seq,
      pass,
      # Line 5
      pass,
      pass,
      # Line 4
      stop]]],

Impact

No vulnerable production contracts were found. Additionally, using a lock on a default function is a very sparsely used pattern. As such, the impact is low.

References

@charles-cooper charles-cooper published to vyperlang/vyper Apr 25, 2024
Published by the National Vulnerability Database Apr 25, 2024
Published to the GitHub Advisory Database Apr 25, 2024
Reviewed Apr 25, 2024
Last updated Apr 25, 2024

Severity

Moderate

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
Low
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:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS score

0.045%
(17th percentile)

Weaknesses

CVE ID

CVE-2024-32648

GHSA ID

GHSA-m2v9-w374-5hj9

Source code

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