ZEBRA: Block suppression via NU5 same-header body poisoning of sent-hash cache
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- None · High · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| ZcashFoundation | zebra | before 4.5.0 | 4.5.0 | Patch available | CNA |
| — | zebra-state (crates.io) | before 7.0.0 | 7.0.0 | Patch available | GHSA-4m69-67m6-prqp |
| — | zebrad (crates.io) | before 4.5.0 | 4.5.0 | Patch available | GHSA-4m69-67m6-prqp |
- zebra VendorZcashFoundation Affected before 4.5.0 Fixed in 4.5.0 Patch available CNA
- zebra-state (crates.io) Vendor— Affected before 7.0.0 Fixed in 7.0.0 Patch available GHSA-4m69-67m6-prqp
- zebrad (crates.io) Vendor— Affected before 4.5.0 Fixed in 4.5.0 Patch available GHSA-4m69-67m6-prqp
Remediation
- Fix · CNA zebra (ZcashFoundation) Fixed in 4.5.0
- Fix · GHSA-4m69-67m6-prqp zebra-state (crates.io) Fixed in 7.0.0 Advisory →
- Fix · GHSA-4m69-67m6-prqp zebrad (crates.io) Fixed in 4.5.0 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-52736
- 2026-10-03 Alias added: GHSA-4m69-67m6-prqp
References
Other 6
- https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-4m69-67m6-prqp
- https://github.com/ZcashFoundation/zebra/commit/1440b43ca7df59aca948090d45117557b217a6cd
- https://github.com/ZcashFoundation/zebra/releases/tag/v4.5.0
- https://github.com/ZcashFoundation/zebra
- https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1ca79fec/zebra-state/src/service.rs#L659-L714
- https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1ca79fec/zebra-state/src/service.rs#L797-L802
More ZcashFoundation vulnerabilities
- TI-2026-66079 Zebra before 4.4.0 Consensus Split via SIGHASH_SINGLE Missing-Output Handling CVSS 4.0HIGH 8.3
- TI-2026-37850 ZEBRA: Mempool transaction admission denial via single-peer inbound queue saturation CVSS 3.1MEDIUM 5.3
- TI-2026-71182 Improper block validation in Zebra gossip lets peers drop new blocks CVSS 4.0MEDIUM 6.3
- TI-2026-29537 Zebra: addr/addrv2 Deserialization Resource Exhaustion CVSS 4.0MEDIUM 6.3
- TI-2026-86702 Incomplete cleanup in Zebra lets peers stall initial sync CVSS 4.0HIGH 8.7
- TI-2026-86701 Quadratic signature hashing in Zcash Zebra enables denial of service CVSS 4.0HIGH 8.7
Sources
- CVE-2026-52736 · CVE Program
- CVE-2026-52736 · NVD
- FIRST EPSS
- GHSA-4m69-67m6-prqp · GitHub Advisory Database · CC BY 4.0
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