{"id":"CVE-2026-52739","aliases":["GHSA-hhm7-qrv5-h4r6"],"url":"https://o3.security/vulnerability/CVE-2026-52739","summary":"ZEBRA: Repeated Non-Finalized Shielded Transaction Aborts Zebra Before Duplicate-Nullifier Rejection","details":"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.","published":"2026-08-18T19:22:19.865Z","modified":"2026-08-21T03:30:24.989909154Z","cvss":{"score":5.9,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":{"score":0.00394,"percentile":0.32637,"asOf":"2026-09-07"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"crates.io","name":"zebra-state","fixedVersion":"7.0.0"},{"ecosystem":"crates.io","name":"zebrad","fixedVersion":"4.5.0"}],"fix":{"url":"https://github.com/ZcashFoundation/zebra/commit/1440b43ca7df59aca948090d45117557b217a6cd","label":"ZcashFoundation/zebra@1440b43"},"references":[{"type":"WEB","url":"https://github.com/ZcashFoundation/zebra/releases/tag/v4.5.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52739.json"},{"type":"ADVISORY","url":"https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-hhm7-qrv5-h4r6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52739"},{"type":"FIX","url":"https://github.com/ZcashFoundation/zebra/commit/1440b43ca7df59aca948090d45117557b217a6cd"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-21T03:30:24.989909154Z"}}