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PYSEC-2023-306

HighCVSS 8.1 / 10
Published Sep 18, 2023·Last modified Nov 21, 2024
Affected Components(0)

No affected components available

Description

Vyper is a Pythonic Smart Contract Language for the Ethereum Virtual Machine (EVM). In version 0.3.9 and prior, under certain conditions, the memory used by the builtins raw_call, create_from_blueprint and create_copy_of can be corrupted. For raw_call, the argument buffer of the call can be corrupted, leading to incorrect calldata in the sub-context. For create_from_blueprint and create_copy_of, the buffer for the to-be-deployed bytecode can be corrupted, leading to deploying incorrect bytecode.

Each builtin has conditions that must be fulfilled for the corruption to happen. For raw_call, the data argument of the builtin must be msg.data and the value or gas passed to the builtin must be some complex expression that results in writing to the memory. For create_copy_of, the value or salt passed to the builtin must be some complex expression that results in writing to the memory. For create_from_blueprint, either no constructor parameters should be passed to the builtin or raw_args should be set to True, and the value or salt passed to the builtin must be some complex expression that results in writing to the memory.

As of time of publication, no patched version exists. The issue is still being investigated, and there might be other cases where the corruption might happen. When the builtin is being called from an internal function F, the issue is not present provided that the function calling F wrote to memory before calling F. As a workaround, the complex expressions that are being passed as kwargs to the builtin should be cached in memory prior to the call to the builtin.

Risk Scores
Base Score
8.1

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.

Threat Intelligence
7.4

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.70%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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