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CVE-2023-42806

Snapshot signature not including HeadID will allow replay attacks

6.5 Medium

Hydra is the layer-two scalability solution for Cardano. Prior to version 0.13.0, not signing and verifying $\mathsf{cid}$ allows an attacker (which must be a participant of this head) to use a snapshot from an old head instance with the same participants to close the head or contest the state with it. This can lead to an incorrect distribution of value (= value extraction attack; hard, but possible) or prevent the head to finalize because the value available is not consistent with the closed utxo state (= denial of service; easy). A patch is planned for version 0.13.0. As a workaround, rotate keys between heads so not to re-use keys and not result in the same multi-signature participants.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
High
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
High

Exploit likelihood

0.52%Up 0.5 points since Sep 22, 2023
90%50%10%1%

What each source reports

CVE List Score used 6.5

Snapshot signature not including HeadID will allow replay attacks

Hydra is the layer-two scalability solution for Cardano. Prior to version 0.13.0, not signing and verifying $\mathsf{cid}$ allows an attacker (which must be a participant of this head) to use a snapshot from an old head instance with the same participants to close the head or contest the state with it. This can lead to an incorrect distribution of value (= value extraction attack; hard, but possible) or prevent the head to finalize because the value available is not consistent with the closed utxo state (= denial of service; easy). A patch is planned for version 0.13.0. As a workaround, rotate keys between heads so not to re-use keys and not result in the same multi-signature participants.

Record
CVE-2023-42806
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-347
Updated
2026-11-02
EUVDEUVD-2023-47232 6.5

Hydra is the layer-two scalability solution for Cardano. Prior to version 0.13.0, not signing and verifying $\mathsf{cid}$ allows an attacker (which must be a participant of this head) to use a snapshot from an old head instance with the same participants to close the head or contest the state with it. This can lead to an incorrect distribution of value (= value extraction attack; hard, but possible) or prevent the head to finalize because the value available is not consistent with the closed utxo state (= denial of service; easy). A patch is planned for version 0.13.0. As a workaround, rotate keys between heads so not to re-use keys and not result in the same multi-signature participants.

Record
EUVD-2023-47232
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
Updated
2026-11-03
NVD 6.5

Hydra is the layer-two scalability solution for Cardano. Prior to version 0.13.0, not signing and verifying $\mathsf{cid}$ allows an attacker (which must be a participant of this head) to use a snapshot from an old head instance with the same participants to close the head or contest the state with it. This can lead to an incorrect distribution of value (= value extraction attack; hard, but possible) or prevent the head to finalize because the value available is not consistent with the closed utxo state (= denial of service; easy). A patch is planned for version 0.13.0. As a workaround, rotate keys between heads so not to re-use keys and not result in the same multi-signature participants.

Record
CVE-2023-42806
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-347
Updated
2026-11-02
OSV 6.5

Snapshot signature not including HeadID will allow replay attacks

Hydra is the layer-two scalability solution for Cardano. Prior to version 0.13.0, not signing and verifying $\mathsf{cid}$ allows an attacker (which must be a participant of this head) to use a snapshot from an old head instance with the same participants to close the head or contest the state with it. This can lead to an incorrect distribution of value (= value extraction attack; hard, but possible) or prevent the head to finalize because the value available is not consistent with the closed utxo state (= denial of service; easy). A patch is planned for version 0.13.0. As a workaround, rotate keys between heads so not to re-use keys and not result in the same multi-signature participants.

Record
CVE-2023-42806
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-347
Updated
2026-11-02

Affected products

History

History
RecordedChangedSources
aliases, products, publishedEUVD
first indexedCVE List, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2023-42806 is a medium vulnerability (CVSS 6.5) in Input-output-hk Hydra, published September 21, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.52%, the 44th percentile. No source names a fixed version.

References

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