CVE-2026-52739: Zcashfoundation Zebra

Medium severity, CVSS 5.9. EPSS: 0.5% chance of exploitation in the next 30 days.

ZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, a malicious block producer can terminate zebrad by placing the same shielded transaction in a non-finalized parent block and its child. In zebra-state/src/service/non_finalized_state/chain.rs, Chain::push originally inserted the transaction hash into tx_loc_by_hash and asserted uniqueness before updating shielded data and running the duplicate Sprout, Sapling, or Orchard nullifier checks. The repeated transaction therefore reached the transactions must be unique within a single chain assertion before contextual validation could reject it cleanly. Zebra release builds use panic equals abort, so the reachable assertion terminates the entire process; exploitation requires either two consecutive attacker-mined blocks or an attacker-mined child immediately after an honest block includes the attacker's shielded transaction. This issue is fixed in version 4.5.0.

Affected products

• Zcashfoundation Zebra: before 4.5.0 (fixed in 4.5.0)
• Zcashfoundation Zebra-State: before 7.0.0 (fixed in 7.0.0)

Published 2026-08-18. Last modified 2026-09-09.