CVE-2023-38701: 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...

Description

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.

Metrics

CVSS 3.1

9.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

EPSS Probability

0.92%

55.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-20

Affected Software

Vendor	Product	Versions
Iohk	Hydra	< 0.12.0

References

Timeline

Published: Oct 4, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-38701?

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.

How severe is CVE-2023-38701?

CVE-2023-38701 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 0.92% probability of exploitation in the next 30 days.

How do I fix CVE-2023-38701?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.