GHSA-22qq-3xwm-r5x4: CometBFT allows a malicious peer to make node stuck in blocksync
Name: ASA-2025-001: Malicious peer can disrupt node's ability to sync via blocksync
Component: CometBFT
[OUTDATED] Criticality: Medium (Considerable Impact; Possible Likelihood per [ACMv1.2](https://github.com/interchainio/security/blob/main/resources/CLASSIFICATION_MATRIX.md))
**Update of Criticality on 2026-03-06**: We've made a mistake and over-rated the criticality of this bug in our initial triage. We have calibrated our vulnerability rating internally and updated the criticality of this bug to be Informational (Negligible Impact, Possible Likelihood)
Affected versions: <= v0.38.16, v1.0.0
Affected users: Validators, Full nodesImpactA malicious peer may be able to interfere with a node's ability to sync blocks with peers via the blocksync mechanism.In the `blocksync` protocol peers send their `base` and `latest` heights when they connect to a new node (`A`), which is syncing to the tip of a network. `base` acts as a lower ground and informs `A` that the peer only has blocks starting from height `base`. `latest` height informs `A` about the latest block in a network. Normally, nodes would only report increasing heights:If `B` fails to provide the latest block, `B` is removed and the `latest` height (target height) is recalculated based on other nodes `latest` heights.The existing code hovewer doesn't check for the case where `B` first reports `latest` height `X` and immediately after height `Y`, where `X > Y`. For example:`A` will be trying to catch up to 2000 indefinitely. Even if `B` disconnects, the `latest` height (target height) won't be recalculated because `A` "doesn't know where 2000" came from per see.Impact QualificationThis condition requires the introduction of malicious code in the full node first reporting a non-existing `latest` height, then reporting lower `latest` height and nodes which are syncing using `blocksync` protocol.PatchesThe new CometBFT releases [v1.0.1](https://github.com/cometbft/cometbft/releases/tag/v1.0.1) and [v0.38.17](https://github.com/cometbft/cometbft/releases/tag/v0.38.17) fix this issue.Unreleased code in the main is patched as well.WorkaroundsWhen the operator notices `blocksync` is stuck, they can identify the peer from which that message with "invalid" height was received. This may require increasing the logging level of the `blocksync` module. This peer can then be subsequently banned at the p2p layer as a temporary mitigation.ReferencesIf you have questions about Interchain security efforts, please reach out to our official communication channel at [security@interchain.io](mailto:security@interchain.io).  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 CometBFT [repository](https://github.com/cometbft/cometbft/security/advisories/GHSA-22qq-3xwm-r5x4). For more information about CometBFT, see https://docs.cometbft.com/.EDIT:Please notice that this has been updated to be `informational` severity.  This can be avoided by ensuring that one is not connected to a malicious peer during blocksync.
CVSS v4.0: 6.9