Denial of Service (DoS) Affecting vyper package, versions [,0.3.8)


Severity

Recommended
0.0
medium
0
10

CVSS assessment made by Snyk's Security Team

    Threat Intelligence

    Exploit Maturity
    Proof of concept
    EPSS
    0.12% (47th percentile)

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  • Snyk ID SNYK-PYTHON-VYPER-5458965
  • published 25 Apr 2023
  • disclosed 24 Apr 2023
  • credit algys, pavelvm5

How to fix?

Upgrade vyper to version 0.3.8 or higher.

Overview

vyper is a Pythonic Smart Contract Language for the EVM.

Affected versions of this package are vulnerable to Denial of Service (DoS) when the max_outsize=0 and revert_on_failure=False the Vyper compiler generates the wrong bytecode. Any contract that uses the raw_call with revert_on_failure=False and max_outsize=0 receives the wrong response from raw_call. Depending on the memory garbage, the result can be either True or False.

Workaround

Use max_outsize>0. Workaround example https://github.com/lidofinance/gate-seals/pull/5/files

PoC

@external
def returnSome(calling: address, a: uint256) -> bool:
    success: bool = false
    success = raw_call(
        calling,
        _abi_encode(a, method_id=method_id("a(uint256)")),
        revert_on_failure=False
        )

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

  • High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

  • Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

References

CVSS Scores

version 3.1
Expand this section

Snyk

Recommended
5.3 medium
  • Attack Vector (AV)
    Network
  • Attack Complexity (AC)
    Low
  • Privileges Required (PR)
    None
  • User Interaction (UI)
    None
  • Scope (S)
    Unchanged
  • Confidentiality (C)
    None
  • Integrity (I)
    None
  • Availability (A)
    Low
Expand this section

NVD

7.5 high