ZcashFoundation Zebra up to 4.4.x Zebra State service.rs queue_and_commit_to_non_finalized_state race condition

Summaryinfo

A vulnerability was found in ZcashFoundation Zebra up to 4.4.x and classified as problematic. Affected is the function queue_and_commit_to_non_finalized_state of the file zebra-state/src/service.rs of the component Zebra State. The manipulation results in race condition. This vulnerability is reported as CVE-2026-52736. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as problematic, was found in ZcashFoundation Zebra up to 4.4.x. Affected is the function queue_and_commit_to_non_finalized_state of the file zebra-state/src/service.rs of the component Zebra State. The manipulation with an unknown input leads to a race condition vulnerability. CWE is classifying the issue as CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. This is going to have an impact on availability. CVE summarizes:

ZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, a remote unauthenticated P2P peer can stall a Zebra node by racing an invalid block body against the valid canonical body for the same block header hash. ZIP-244 permits the attacker to mutate coinbase scriptSig authentication data while retaining the transaction identifiers, merkle root, and block header hash, so the poisoned body fails later commitment validation but shares the canonical hash. In zebra-state/src/service.rs, queue_and_commit_to_non_finalized_state recorded the hash in non_finalized_block_write_sent_hashes before contextual validation completed and did not remove it when the write task rejected the body. When the honest body later arrived, the cached hash caused KnownBlock::WriteChannel duplicate handling to suppress it, leaving the node stuck one height behind until restart or reorganization. This issue is fixed in version 4.5.0.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-52736 since 06/08/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit.

Upgrading to version 4.5.0 eliminates this vulnerability.

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Productinfo

Vendor

• ZcashFoundation

Name

• Zebra

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4

Website

• Product: https://github.com/ZcashFoundation/zebra/

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