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IBC-Go has Non-deterministic JSON Unmarshalling of IBC Acknowledgement

Critical severity GitHub Reviewed Published Feb 27, 2025 in cosmos/ibc-go • Updated Feb 28, 2025

Package

gomod github.com/cosmos/ibc-go (Go)

Affected versions

< 7.9.2

Patched versions

None
gomod github.com/cosmos/ibc-go/v2 (Go)
< 7.9.2
None
gomod github.com/cosmos/ibc-go/v3 (Go)
< 7.9.2
None
gomod github.com/cosmos/ibc-go/v4 (Go)
< 7.9.2
None
gomod github.com/cosmos/ibc-go/v5 (Go)
< 7.9.2
None
gomod github.com/cosmos/ibc-go/v6 (Go)
< 7.9.2
None
gomod github.com/cosmos/ibc-go/v7 (Go)
< 7.9.2
7.9.2
gomod github.com/cosmos/ibc-go/v8 (Go)
< 8.6.1
8.6.1

Description

Name: ASA-2025-004: Non-deterministic JSON Unmarshalling of IBC Acknowledgement can result in a chain halt
Component: IBC-Go
Criticality: Critical (Considerable Impact; Almost Certain Likelihood per ACMv1.2)
Affected versions: IBC-Go >= v7; Earlier IBC-Go versions may also be affected.
Affected users: Validators, Full nodes, IBC Middleware authors

Description

An issue was discovered in IBC-Go's deserialization of acknowledgements that results in non-deterministic behavior which can halt a chain. Any user that can open an IBC channel can introduce this state to the chain

Patches

The new IBC-Go releases below address this issue:

Workarounds

To prevent this state from being introduced to a chain, it is possible to permission Channel Opening as a workaround.

Notes on Re-Release

Is this state breaking? Probably not but it depends on your transfer middlewares

This patch is not state breaking unless you depend on transfer middlewares that deserialize and serialize acknowledgement packets before passing them to the transfer handler. As far as we can tell, these middlewares are rare. For example, packet-forward-middleware and ibc-hooks, do not serialize ack packets in this way and therefore aren't broken by this patch. So if these are the only transfer middlewares you depend on, you can safely apply this patch in a rolling manner (and we've already cut new versions of these for you).

What to do if you do depend on ack-serializing middleware

In the unlikely case that you depend on middlewares that serialize ack packets and you do not update them when you apply this patch, all transfers that are handled by the middleware will fail (or experience other unexpected behavior) if the serialization approach differs from the transfer app's. If you have such dependencies and do not update them, validators who apply the patch in a rolling manner will halt when they upgrade, and transfers processed by the middleware will just fail once everyone has upgraded.

To update these middlewares and avoid failing transfers or a chain halt, you will simply need to change the serialization approach in the middleware to use ibc-go's codec: transfertypes.ModuleCdc.[Must]MarshalJSON, rather than whatever you're doing today. For example:

import transfertypes "github.com/cosmos/ibc-go/v10/modules/apps/transfer/types"
transfertypes.ModuleCdc.[Must]MarshalJSON
func MarshalAsIBCDoes(ack channeltypes.Acknowledgement) ([]byte, error) {
	return transfertypes.ModuleCdc.MarshalJSON(&ack)
}

When you do make a change to the serialization approach, this will make the patch state breaking and you will need a coordinated upgrade. So for absolute clarity: chains with these ack-serializing middlewares must do coordinated upgrades

Why we retracted the earlier patch in favor of this approach

We retracted the releases of ibc-go we cut earlier today because these broke all transfer middlewares that deserialized then re-serialized receive packets differently than the transfer app. It turned out that this was a common pattern (unlike serializing/deserializing ack packets), so widely used middlewares, including packet-forward-middleware, broke unexpectedly.

In the new set of patches, we removed this constraint on how middlewares serialize receive packets, preventing this breakage. Only the serialization requirement on acknowledgement packets remains. This is convenient because this is the only constraint we had to add to fix the vulnerability, and middlewares that deserialize and serialize ack packets are much less common than ones that do so for receive packets. The constraint on receive packets was added for defense in depth.

Testing we have done to gain more confidence in this release

  • In addition to testing ibc-go, we also did the following:
  • Tested pfm v7 and v8 after bumping dependencies
  • Tested ibc-hooks v7 and v8 after bumping dependencies
  • Ran a patched node on mainnet on the cosmos hub and triggered failing and successful transactions that used PFM
  • Ran a patched node on osmosis and triggered failing and successful transactions that used ibc-hooks
    This is a more thorough process than before, so we have higher confidence.

Timeline

  • February 18, 2025, 4:54am PST: Issue reported to the Cosmos Bug Bounty program
  • February 18, 2025, 6:56am PST: Issue triaged by Amulet on-call, and distributed to Core team
  • February 18, 2025, 8:15am PST: Core team completes validation of issue
  • February 25, 2025, 8:00am PST / 17:00 CET: Pre-notification delivered
  • February 27, 2025, 8:00am PST / 17:00 CET: Patch made available
  • February 27, 2025, 1:00pm PST: Patch re-release made available

This issue was reported to the Cosmos Bug Bounty Program by swelf19 on HackerOne on February 18, 2025. If you believe you have found a bug in the Interchain Stack or would like to contribute to the program by reporting a bug, please see https://hackerone.com/cosmos.

If you have questions about Interchain security efforts, please reach out to our official communication channel at [email protected]. For more information about the Interchain Foundation’s engagement with Amulet, and to sign up for security notification emails, please see https://github.com/interchainio/security.

A Github Security Advisory for this issue is available in the IBC-Go repository.

References

@Zygimantass Zygimantass published to cosmos/ibc-go Feb 27, 2025
Published to the GitHub Advisory Database Feb 28, 2025
Reviewed Feb 28, 2025
Last updated Feb 28, 2025

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

EPSS score

Weaknesses

CVE ID

No known CVE

GHSA ID

GHSA-jg6f-48ff-5xrw

Source code

Credits

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