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CVE-2023-38701

Hydra's committed UTxOs at Commit validator and UTxOs at Initial validator can be spent arbitrarily by anyone

9.1 Critical

CVE-2023-38701 is a critical vulnerability (CVSS 9.1) in Input-output-hk Hydra, published October 4, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.13%, the 66th percentile. No source names a fixed version.

Hydra is the layer-two scalability solution for Cardano. Users of the Hydra head protocol send the UTxOs they wish to commit into the Hydra head first to the commit validator, where they remain until they are either collected into the head validator or the protocol initialisation is aborted and the value in the committed UTxOs is returned to the users who committed them. Prior to version 0.12.0, the commit validator contains a flawed check when the ViaAbort redeemer is used, which allows any user to spend any UTxO which is at the validator arbitrarily, meaning an attacker can steal the funds that users are trying to commit into the head validator. The intended behavior is that the funds must be returned to the user which committed the funds and can only be performed by a participant of the head. The initial validator also is similarly affected as the same flawed check is performed for the ViaAbort redeemer. Due to this issue, an attacker can steal any funds that user's try to commit into a Hydra head. Also, an attacker can prevent any Hydra head from being successfully opened. It does not allow an attacker to take funds which have been successfully collected into and currently reside in the head validator. Version 0.12.0 contains a fix for this issue.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
High

Exploit likelihood

1.13%Up 1.1 points since Oct 5, 2023
90%50%10%1%

What each source reports

CVE List Score used 9.1

Hydra's committed UTxOs at Commit validator and UTxOs at Initial validator can be spent arbitrarily by anyone

Hydra is the layer-two scalability solution for Cardano. Users of the Hydra head protocol send the UTxOs they wish to commit into the Hydra head first to the commit validator, where they remain until they are either collected into the head validator or the protocol initialisation is aborted and the value in the committed UTxOs is returned to the users who committed them. Prior to version 0.12.0, the commit validator contains a flawed check when the ViaAbort redeemer is used, which allows any user to spend any UTxO which is at the validator arbitrarily, meaning an attacker can steal the funds that users are trying to commit into the head validator. The intended behavior is that the funds must be returned to the user which committed the funds and can only be performed by a participant of the head. The initial validator also is similarly affected as the same flawed check is performed for the ViaAbort redeemer. Due to this issue, an attacker can steal any funds that user's try to commit into a Hydra head. Also, an attacker can prevent any Hydra head from being successfully opened. It does not allow an attacker to take funds which have been successfully collected into and currently reside in the head validator. Version 0.12.0 contains a fix for this issue.

Record
CVE-2023-38701
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-20
Updated
2026-11-02
EUVDEUVD-2023-42478 9.1

Hydra is the layer-two scalability solution for Cardano. Users of the Hydra head protocol send the UTxOs they wish to commit into the Hydra head first to the commit validator, where they remain until they are either collected into the head validator or the protocol initialisation is aborted and the value in the committed UTxOs is returned to the users who committed them. Prior to version 0.12.0, the commit validator contains a flawed check when the ViaAbort redeemer is used, which allows any user to spend any UTxO which is at the validator arbitrarily, meaning an attacker can steal the funds that users are trying to commit into the head validator. The intended behavior is that the funds must be returned to the user which committed the funds and can only be performed by a participant of the head. The initial validator also is similarly affected as the same flawed check is performed for the ViaAbort redeemer. Due to this issue, an attacker can steal any funds that user's try to commit into a Hydra head. Also, an attacker can prevent any Hydra head from being successfully opened. It does not allow an attacker to take funds which have been successfully collected into and currently reside in the head validator. Version 0.12.0 contains a fix for this issue.

Record
EUVD-2023-42478
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Updated
2026-11-03
NVD 9.1

Hydra is the layer-two scalability solution for Cardano. Users of the Hydra head protocol send the UTxOs they wish to commit into the Hydra head first to the commit validator, where they remain until they are either collected into the head validator or the protocol initialisation is aborted and the value in the committed UTxOs is returned to the users who committed them. Prior to version 0.12.0, the commit validator contains a flawed check when the ViaAbort redeemer is used, which allows any user to spend any UTxO which is at the validator arbitrarily, meaning an attacker can steal the funds that users are trying to commit into the head validator. The intended behavior is that the funds must be returned to the user which committed the funds and can only be performed by a participant of the head. The initial validator also is similarly affected as the same flawed check is performed for the ViaAbort redeemer. Due to this issue, an attacker can steal any funds that user's try to commit into a Hydra head. Also, an attacker can prevent any Hydra head from being successfully opened. It does not allow an attacker to take funds which have been successfully collected into and currently reside in the head validator. Version 0.12.0 contains a fix for this issue.

Record
CVE-2023-38701
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-20
Updated
2026-11-02
OSV 9.1

Hydra's committed UTxOs at Commit validator and UTxOs at Initial validator can be spent arbitrarily by anyone

Hydra is the layer-two scalability solution for Cardano. Users of the Hydra head protocol send the UTxOs they wish to commit into the Hydra head first to the commit validator, where they remain until they are either collected into the head validator or the protocol initialisation is aborted and the value in the committed UTxOs is returned to the users who committed them. Prior to version 0.12.0, the commit validator contains a flawed check when the ViaAbort redeemer is used, which allows any user to spend any UTxO which is at the validator arbitrarily, meaning an attacker can steal the funds that users are trying to commit into the head validator. The intended behavior is that the funds must be returned to the user which committed the funds and can only be performed by a participant of the head. The initial validator also is similarly affected as the same flawed check is performed for the ViaAbort redeemer. Due to this issue, an attacker can steal any funds that user's try to commit into a Hydra head. Also, an attacker can prevent any Hydra head from being successfully opened. It does not allow an attacker to take funds which have been successfully collected into and currently reside in the head validator. Version 0.12.0 contains a fix for this issue.

Record
CVE-2023-38701
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-20
Updated
2026-11-02

Affected products

History

History
WhenChangedSources
2026-11-03aliases, products, publishedEUVD
2026-11-02createdCVE List, NVD, OSV

References

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