CVE-2025-52884

RISC Zero is a zero-knowledge verifiable general computing platform, with Ethereum integration. The risc0-ethereum repository contains Solidity verifier contracts, Steel EVM view call library, and supporting code. Prior to versions 2.1.1 and 2.2.0, the Steel.validateCommitment Solidity library function will return true for a crafted commitment with a digest value of zero. This violates the semantics of validateCommitment, as this does not commitment to a block that is in the current chain. Because the digest is zero, it does not correspond to any block and there exist no known openings. As a result, this commitment will never be produced by a correct zkVM guest using Steel and leveraging this bug to compromise the soundness of a program using Steel would require a separate bug or misuse of the Steel library, which is expected to be used to validate the root of state opening proofs. A fix has been released as part of risc0-ethereum 2.1.1 and 2.2.0. Users for the Steel Solidity library versions 2.1.0 or earlier should ensure they are using Steel.validateCommitment in tandem with zkVM proof verification of a Steel program, as shown in the ERC-20 counter example, and documentation. This is the correct usage of Steel, and users following this pattern are not at risk, and do not need to take action. Users not verifying a zkVM proof of a Steel program should update their application to do so, as this is incorrect usage of Steel.

RISC Zero is a zero-knowledge verifiable general computing platform, with Ethereum integration. The risc0-ethereum repository contains Solidity verifier contracts, Steel EVM view call library, and supporting code. Prior to versions 2.1.1 and 2.2.0, the Steel.validateCommitment Solidity library function will return true for a crafted commitment with a digest value of zero. This violates the semantics of validateCommitment, as this does not commitment to a block that is in the current chain. Because the digest is zero, it does not correspond to any block and there exist no known openings. As a result, this commitment will never be produced by a correct zkVM guest using Steel and leveraging this bug to compromise the soundness of a program using Steel would require a separate bug or misuse of the Steel library, which is expected to be used to validate the root of state opening proofs. A fix has been released as part of risc0-ethereum 2.1.1 and 2.2.0. Users for the Steel Solidity library versions 2.1.0 or earlier should ensure they are using Steel.validateCommitment in tandem with zkVM proof verification of a Steel program, as shown in the ERC-20 counter example, and documentation. This is the correct usage of Steel, and users following this pattern are not at risk, and do not need to take action. Users not verifying a zkVM proof of a Steel program should update their application to do so, as this is incorrect usage of Steel.

Impact

Prior to 2.1.1 and 2.2.0, the Steel.validateCommitment Solidity library function will return true for a crafted commitment with a digest value of zero.

This violates the semantics of validateCommitment, as this does not commitment to a block that is in the current chain. Because the digest is zero, it does not correspond to any block and there exist no known openings. As a result, this commitment will never be produced by a correct zkVM guest using Steel. Leveraging this bug to compromise the soundness of an application using Steel would require a separate bug or misuse of the Steel library, which is expected to be used to validate the root of state opening proofs (e.g. having the guest commit to a digest of zero, or failing to check the zkVM proof).

Because this bug does not risk application integrity, correctly written applications are not at risk.

Fix

Please see #605 for a full description of the bug, and the fix. This fix has been released as part of risc0-ethereum 2.1.1 and 2.2.0.

Recommended actions

Users for the Steel Solidity library versions 2.1.0 or earlier should ensure they are using Steel.validateCommitment in tandem with zkVM proof verification of a Steel program, as shown in the ERC-20 counter example, and documentation. This is the correct usage of Steel, and users following this pattern are not at risk, and do not need to take action.

Users not verifying a zkVM proof of a Steel program should update their application to do so, as this is incorrect usage of Steel.

Credit

A thank you to Daniel526 on HackenProof for reporting this issue

RISC Zero is a zero-knowledge verifiable general computing platform, with Ethereum integration. The risc0-ethereum repository contains Solidity verifier contracts, Steel EVM view call library, and supporting code. Prior to versions 2.1.1 and 2.2.0, the Steel.validateCommitment Solidity library function will return true for a crafted commitment with a digest value of zero. This violates the semantics of validateCommitment, as this does not commitment to a block that is in the current chain. Because the digest is zero, it does not correspond to any block and there exist no known openings. As a result, this commitment will never be produced by a correct zkVM guest using Steel and leveraging this bug to compromise the soundness of a program using Steel would require a separate bug or misuse of the Steel library, which is expected to be used to validate the root of state opening proofs. A fix has been released as part of risc0-ethereum 2.1.1 and 2.2.0. Users for the Steel Solidity library versions 2.1.0 or earlier should ensure they are using Steel.validateCommitment in tandem with zkVM proof verification of a Steel program, as shown in the ERC-20 counter example, and documentation. This is the correct usage of Steel, and users following this pattern are not at risk, and do not need to take action. Users not verifying a zkVM proof of a Steel program should update their application to do so, as this is incorrect usage of Steel.

RISC Zero is a zero-knowledge verifiable general computing platform, with Ethereum integration. The risc0-ethereum repository contains Solidity verifier contracts, Steel EVM view call library, and supporting code. Prior to versions 2.1.1 and 2.2.0, the Steel.validateCommitment Solidity library function will return true for a crafted commitment with a digest value of zero. This violates the semantics of validateCommitment, as this does not commitment to a block that is in the current chain. Because the digest is zero, it does not correspond to any block and there exist no known openings. As a result, this commitment will never be produced by a correct zkVM guest using Steel and leveraging this bug to compromise the soundness of a program using Steel would require a separate bug or misuse of the Steel library, which is expected to be used to validate the root of state opening proofs. A fix has been released as part of risc0-ethereum 2.1.1 and 2.2.0. Users for the Steel Solidity library versions 2.1.0 or earlier should ensure they are using Steel.validateCommitment in tandem with zkVM proof verification of a Steel program, as shown in the ERC-20 counter example, and documentation. This is the correct usage of Steel, and users following this pattern are not at risk, and do not need to take action. Users not verifying a zkVM proof of a Steel program should update their application to do so, as this is incorrect usage of Steel.

Impact

Prior to 2.1.1 and 2.2.0, the Steel.validateCommitment Solidity library function will return true for a crafted commitment with a digest value of zero.

This violates the semantics of validateCommitment, as this does not commitment to a block that is in the current chain. Because the digest is zero, it does not correspond to any block and there exist no known openings. As a result, this commitment will never be produced by a correct zkVM guest using Steel. Leveraging this bug to compromise the soundness of an application using Steel would require a separate bug or misuse of the Steel library, which is expected to be used to validate the root of state opening proofs (e.g. having the guest commit to a digest of zero, or failing to check the zkVM proof).

Because this bug does not risk application integrity, correctly written applications are not at risk.

Fix

Please see #605 for a full description of the bug, and the fix. This fix has been released as part of risc0-ethereum 2.1.1 and 2.2.0.

Recommended actions

Users for the Steel Solidity library versions 2.1.0 or earlier should ensure they are using Steel.validateCommitment in tandem with zkVM proof verification of a Steel program, as shown in the ERC-20 counter example, and documentation. This is the correct usage of Steel, and users following this pattern are not at risk, and do not need to take action.

Users not verifying a zkVM proof of a Steel program should update their application to do so, as this is incorrect usage of Steel.

Credit

A thank you to Daniel526 on HackenProof for reporting this issue