{"id":"CVE-2026-52732","aliases":["GHSA-4fc2-h7jh-287c"],"url":"https://o3.security/vulnerability/CVE-2026-52732","summary":"ZEBRA: Mempool transaction admission denial via single-peer inbound queue saturation","details":"ZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, one unauthenticated P2P peer can monopolize all 25 MAX_INBOUND_CONCURRENCY slots in Zebra's inbound mempool download and verification pipeline. In zebrad/src/components/mempool/downloads.rs, the bounded queue was shared globally without per-peer accounting, while peer identity was not carried through Gossip and FullQueue responses were mapped to Response::Nil instead of reaching overload disconnection handling. An attacker can advertise fake transaction identifiers and remain silent so each task holds a slot until TRANSACTION_DOWNLOAD_TIMEOUT, then periodically refill the queue as slots expire. While saturated, honest peer transactions and local sendrawtransaction requests are rejected with MempoolError::FullQueue, although block validation and synchronization continue. This issue is fixed in version 4.5.0.","published":"2026-08-18T19:26:07.345Z","modified":"2026-09-11T03:30:22.111010165Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"epss":{"score":0.00371,"percentile":0.30778,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"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-2026-52732.json"},{"type":"ADVISORY","url":"https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-4fc2-h7jh-287c"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52732"},{"type":"FIX","url":"https://github.com/ZcashFoundation/zebra/commit/1440b43ca7df59aca948090d45117557b217a6cd"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-11T03:30:22.111010165Z"}}