CVE-2026-52736 ZEBRA: Block suppression via NU5 same-header body poisoning of sent-hash cache
A remote attacker can stall a Zcash node by racing invalid block bodies against valid ones, causing the node to reject honest blocks and halt synchronization.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-52736?
CVE-2026-52736 is a high-severity vulnerability in ZcashFoundation zebra, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-459
Which versions are affected by CVE-2026-52736?
4 open source packages ship an affected version, including zebra-state and zebrad.
| Package | Affected | Fixed in |
|---|---|---|
zebra-state crates.io | All versions | 7.0.0 |
zebra-state crates.io | All versions | 7.0.0 |
zebrad crates.io | All versions | 4.5.0 |
zebrad crates.io | All versions | 4.5.0 |
How do I fix CVE-2026-52736?
Upgrade zebra-state to 7.0.0 or later.
Is CVE-2026-52736 being exploited?
There is no known exploitation of CVE-2026-52736 in the wild and no public exploit code.
Sources
Also known as GHSA-4m69-67m6-prqp.