CVE-2026-52732 — ZEBRA: Mempool transaction admission denial via single-peer inbound queue saturation

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
ZcashFoundation / zebra	affected < 4.5.0

CWE

CWE-770

References

ADP enrichment

CISA-ADP

No English description supplied.

https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-4fc2-h7jh-287c