GHSA-29h2-jr22-frmh: Npm/@openzeppelin/confidential-contracts vulnerability
Impact
Two locations consume an encrypted handle returned by an untrusted external party and use it without verifying that the party is ACL-authorized on it.
VestingWalletConfidential
Malicious users can call release with a malicious token. This token could return an alternative handle on confidentialBalanceOf, which represents the balance of the vesting wallet on an alternative ERC-7984 token (or any other handle that the vesting wallet has access to). The vesting wallet does not check that the token has ACL access and grants access to a new handle derived from the returned handle.
Effectively, this bug allows a malicious user to gain information about any private euint64 handle that the vesting wallet has access to via a malicious ERC-7984 token. There is no loss of funds.
ERC7984
On a transfer with callback, ERC7984 uses the ebool returned by the recipient's IERC7984Receiver.onConfidentialTransferReceived to drive the refund logic, without checking that the recipient has ACL access to it. A malicious recipient can return any ebool the token has access to and recover its plaintext from the refund result, which the token grants the caller access to. The leak is limited to ebool handles (the value is only used as an FHE.select condition), and there is no loss of funds.
Patches
Both issues were fixed in the same patch releases: v0.5.2, v0.4.2, v0.3.2
- VestingWalletConfidential: 93e75ceed2b9648f53f9d133f431064353456805 (#423). - ERC7984 transfer callback: fe0863af2c9dce7614acce98720a913bf6a767a5 (#428), with follow-up ee47edf189ab681cebdad18bfb53dee541987be2 (#431) permitting an uninitialized returned handle.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/@openzeppelin/confidential-contractsto a version that resolves this vulnerability.Fixed in 0.5.2 - Upgrade
Upgrade
npm/@openzeppelin/confidential-contractsto a version that resolves this vulnerability.Fixed in 0.4.2 - Upgrade
Upgrade
npm/@openzeppelin/confidential-contractsto a version that resolves this vulnerability.Fixed in 0.3.2 - Upgrade
Upgrade
ERC7984 and VestingWalletConfidentialto a version that resolves this vulnerability.Fixed in v0.5.2 - Upgrade
Upgrade
ERC7984 and VestingWalletConfidentialto a version that resolves this vulnerability.Fixed in v0.4.2 - Upgrade
Upgrade
ERC7984 and VestingWalletConfidentialto a version that resolves this vulnerability.Fixed in v0.3.2
Event History
Frequently Asked Questions
What does an attacker need to exploit the VestingWalletConfidential issue?
The attacker needs to call release with a malicious token whose confidentialBalanceOf response supplies an alternative handle that the vesting wallet can access. The issue can expose information about private euint64 handles available to the vesting wallet, but does not cause loss of funds.
What does an attacker need to exploit the ERC7984 callback issue?
The attacker needs to act as a malicious transfer recipient and return an ebool that the token can access from onConfidentialTransferReceived. The token then uses that value in refund logic and grants the caller access to the refund result, allowing recovery of its plaintext.
Are legitimate tokens or recipients necessarily affected?
The described attacks rely on malicious external parties supplying handles without ACL authorization checks. The advisory does not state that ordinary transfers or release calls involving trusted, ACL-authorized counterparties expose data.