CVE-2023-42806
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.
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
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 Medium
CVSS: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 Medium
CVSS: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 Medium
CVSS: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 Medium
CVSS: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
| Recorded | Changed | Sources |
|---|---|---|
| aliases, products, published | EUVD | |
| first indexed | CVE 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
github.com/input-output-hk/hydra/security/advisories/GHSA-gr36-mc6v-72qq
github.com/input-output-hk/hydra/blob/ec6c7a2ab651462228475d0b34264e9a182c22bb/hydra-node/src/Hydra/HeadLogic.hs
github.com/input-output-hk/hydra/blob/ec6c7a2ab651462228475d0b34264e9a182c22bb/hydra-node/src/Hydra/Snapshot.hs
github.com/input-output-hk/hydra/blob/ec6c7a2ab651462228475d0b34264e9a182c22bb/hydra-plutus/src/Hydra/Contract/Head.hs
github.com/CVEProject/cvelistV5/tree/main/cves/2023/42xxx/CVE-2023-42806.json
nvd.nist.gov/vuln/detail/CVE-2023-42806