VulnerabilityDeferred

CVE-2026-52739

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.

MEDIUM 5.9EPSS 0.39%

Does this matter?

Lower severity and a low EPSS score (0.39%). Track it; it rarely justifies an emergency change on its own.

Description

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.

CVSS 3.1: 5.9 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.39% probability · 33th percentile
CISA KEV: Not listed
Weakness: CWE-248
Source: security-advisories@github.com

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.